The larger paint guns are great if you have the skill, but if your worried about getting uniform color a small gun is the best way to go about it. Several light coats. Work on your consistency with each coat, but by them time you have 4 or 5 light ones on there you should have a nice even coat.
Get some craft paper and good masking tape. Just tape off if you want a distinct line, if you want a fade there is no masking. Look up “rail tool” in the archives for info on how to get an even rail line.