all right so i have done a paint brush job on RID PRIME cliffjumper and i found that there is spots where i go over what i have all ready done that make darker marks i was woundering if i use air brushs would i be able to avoid this and are then any other benefits of brush over air brush or visa versa
Both are skills that require practice. It sounds like a paint issue try citadel it is more forgiving. You can run into the same problem spraying. Both below are 100% brush painted. My point is do not stop practicing brush painting both brushing and spraying are valid methods if you attempt to master both your work will be better in the long run.
Exactly what the above posters said. Model Master tends to leave those dark spots you mentioned though I've noticed. Airbrushing avoids it but it comes with it's own problems as well. Brushing is easier IMO and I generally don't have to mask anything off or disassemble the figure where if I were airbushing I would. One thing is to not stop in the middle while brushing, go straight through to the edge or use a wide brush on large areas. Good luck.
Practice will be key in either case. I mean if nothing else, take a couple of toy cars or something, preferably one that's metal & one that's plastic. Experiment a little with both using different sized brushes, especially areas that you remember having less than perfect results with on your Cliffjumper. Wide areas such as on the chest can be challenging, but you'll learn a good form once you experiment lots, and again, primer makes your job 10x easier in the long run. Then when it comes to the brushes themselves, make sure to clean em as soon as possible when you finish. This probably goes without saying, but having a brush that's nice goes a LONG way, and its just (if not more) important than using the right size & strength for the job.