I started doing my customs has a new hobby and I thoroughly enjoy it. My goal is make new characters to have a large “cast” for the picture comics in my head. Check my sig for a few guidelines about my customs you should know. Not any particular order of completion. Hosehead from RID Spychanger Optimus Prime. Nightbeat from RID Spychanger Ironhide. Siren from RID Spychanger Prowl. I know Nighbeat isn't a truck, but it rounded out the set.
There are a lot of really really good ideas here. the biggest advice I'd give is thin your paints and take your time. (well, and sand the scrapey joints).