I havent done any model building in years, but I paint cars for a living. You'd be amazed how well Vasiline works works for lil masking areas where tape wont stick or can get tape samll enough. Lil bit on a brush , q-tip, or dental glue brush.Try it out ,wipes right off, Pam works too.
I use these for droping a lil clear in a fish eye or just lil touch up.
Dental glue brush