I did Warhammer (mostly 40k) back in the day, so I still have some supplies. I have never worked on toys, only models and small figurines/game pieces.
I need suggestions on the cheapest options without sacrificing too much quality.

I have a hobby knife and a pack of #2 blades.

I have an old dremel that doesn't work. I think it's just that the battery no longer holds a charge. Can you get a new battery for an old dremel? If not, what are my cheapest options for a new one?

Dremel bits: I have a couple of sandpaper bits and a set of 7 drill bits from 1/32" to 1/8"
Probably won't ever need them but I still have a bunch of magnets that fit exactly in the hole the largest drill bit makes.
I have several sets of tweezers and I think enough paint brushes to get me started.

Files? I was looking on the Toyhax site and they sell 5 different files...I don't know what the difference is. What kind of files do I need and where's a good place to get them?

Paint: Is it possible to resurrect 10-15 year old citadel paint? I have rehydrated old paint before but not on this time scale. I hope at least some of it is still viable because I have over 30 colors and some of them I never even opened.
What are good brands of not expensive paint for Transformers figures?

Glue: Please recommend me a good glue that both works for the figures and doesn't require 10 minutes of poking and cutting the bottle to get the glue to come out.

What other useful items should I get for my tool kit?

 

Here are 2 examples of my old work to give you an idea of my skill level and what I'm used to working with. Please forgive my subpar camera and lighting.

 

I'm no expert but im having fun using acrylic paints and brushes.
No airbrush, no enamels.
Acrylics are easier to work with but enamels will be more durable, and since we're talking transforming figures you want the paint to last (unless you never play/transform your figs then it doesnt matter) otherwise get a clear finish (brush-on or spraycan) to protect the paint.
And as i said in my Studio Series 38 OP project, definitely use primer, Rustoleum has a for plastics primer in both spraycan or brush on.
Whatever type of paint you choose get a basic color set to get started, most TFs use basic colors and any combination of will get you close to matching a figure's colors. Throw in some metallic paints like silver, chrome, gold.

You dont need super expensive brushes, but dirt cheap ones i would avoid (the bristles will come off the brush and get stuck in the paint). But get a variety of brush sizes. From super thin for those fine detailed areas to flat brushes to go over large areas.

Im an impatient guy so i buy in bulk lol but i would suggest develop a game plan before buying additional supplies. Like if youre going to buy more paints then think of the figure you're going to work on next and buy the paints you need for that figure only.

 

Oh yeah, and watch plenty of youtube videos, but not only custom transformer videos. Guys who custom paint Gundams are also great to watch (same principles as painting a TF)

 

I'm good with basic painting. I have limited experience with ink washing and I was always really bad at drybrushing. I'm more worried about modifying the figures.
Also what brands of paint and glue to get?
Anyone having any experience rehydrating old citadel paints? Worth the try?

 

i cant help you on the rehydrating paints, sorry.
As for what brands? thats up to your budget, really. My local art store carries one specific brand. If i go to Michaels i'll have a wider choice. I just pick a color I need regardless of brand. But i guess for acrylics the preferred brand is Tamiya and Testors for enamels?

 

Anyone on the rehydrating old paints question?

Could really use a good glue brand suggestion too. Last time I bought 2 little tubes of Loctite. The first was like usual where every time I used it, I had to spend 5-10 with a knife/poking implement to get the glue flowing again eventually resulting in the tube busting and glue all over my fingers. The second tube I used once and when I went to use it again a week later, ALL of the remaining glue was completely solid.

 

Harbor Freight is your friend if you want to get tools on a budget. They have precision plier, screwdriver, and file sets. Their heavy duty corded rotary tool works great, if you want to use one. I got a cheap flexible shaft extension for mine from Amazon, though I can't find the one I bought anymore. There are probably others available that are comparable. Their dental pick set looks useful but it's always sold out when I try to get it. Their small spring and quick release clamps help with toy work a lot. They also have inexpensive epoxies and CA glue that work well.

For other tools, I recommend getting a pack of emery boards, some toothpicks, flush-cutters (mine are made by Klein tools and bought from Home Depot), and a thin-kerf saw (I think mine is a Zona saw with a .008 inch kerf). 91% isopropyl and Q-tips are good for removing paint. I also keep some 5-second fix and some plumber's epoxy putty around to build up or fill in parts.

Pledge floor finish is wonderful stuff for many things, many detailed on the tutorials page under the name Future Polish (it's been rebranded since then). I use it to thin regular craft paints for my projects, at a ratio of 3 parts paint to 1 part finish and 1 part water. That mix won't streak like straight craft paint, resists pooling, and cures pretty hard, possibly acting as its own clear coat. It's magic.

As for recovering your old paints, you can probably do that by mixing in some paint thinner. I've never done it but I read that people do that.