roll on or brush for touch ups ?
 

I see lots of stuff for rustoleum roll on paint jobs but was trying to find a roll on or brush on with real automotive paint, not a bc/cc but acrilic enamel. I just need to do some touch up areas inside on my blazer and in behind the wheelwell side panels which are covered anyway. I would like the matching color but don,t what to mask off the the whole interior for this. Would I mix the paint the same as for spraying or a little thicker so no runs ?