Believe it or not but Elmer's glue is the subject here. Larry tells the easiest and cheapest way to get that multicolor paint job done without the headaches of TAPE. First paint your base coat then apply glue to body , then using a hobby knife cut the glue along the pattern you are using (in photos we use the door) gently peal away dried glue and spray your color. After paint dries cover painted area with glue , and repeat for second color and so on . after the final color has dried you can peal away all the dried glue and you will have a multicolored paint job with no separation .
The dry glue peals off easily
Use your hobby knife to cut an edge for the paint & glue peals away up to the edge