put it on in several thin coats and build it up. if you put on just one thick coat it has a tendency to pool in the low spots on the body.
I brush it on at least 4 coats with either a sponge brush or a 1/2 inch bristle brush.
another tip when brushing it on is to apply it in alternating directions for each coat give it a bit more holding power when it's time to remove the mask.
and you do want to lightly scuff the body before you wash it to give the LMF somthing to hang on to. ofcourse if your using chrome you will want to skip this step as it will give the chrome a brushed finish.
another point of info the Parma and Hobbico LMF both suck! stay away from them the bob divley's is the best out there.
If you want to spray it on with the airbrush you'll need to strain it so the lumps don't clog your brush, cheese cloth works great. if you do spray it on you'll need to do about 10 coats as it goes on quite thin but the drying time between coats is much shorter.