first, i would recommend not using the regular blue painters tape. find the one with low tack even then you might want to place it on your pant leg to reduce the tack or buy some tamiya(or the like) hobby tape.
hand brushing it after your done with the exterior would probably be the easiest to do. since you wont have to worry about over spray on the body. but if you have an airbrush, you can mask from the inside and spray it.