Vinyl, as we explained before, is very soft, so masking the parts with tape not only might rip off delicate paint, but angling the cutter to trace patterns on the tape might cut through and scratch the the vinyl. So you have to suck it up and use a brush. Mix some retarder into the paint (not more than 10%) and paint away
If something doesn't fit right, don't be afraid to help it out with a cutter and putty. In this model's case, because the shoulder part's entry hole was molded a little too low, a 3mm cut had to be made to facilitate entry of the arm into the shoulder, and putty added to raise the arm. This is a very delicate process, and seems to be model specific (the manufacturer mentioned that the arm might not fit quite right themselves). If you have a bit of experience then go ahead and fix manufacturer mistakes.
Finally, have fun looking at your pretty little soft vinyl kit!
