Rutan,
Hard to say what has exactly caused your problems, but here's what I'd do if painting a car yellow.
1. Sand with 600-800 grit paper (gives good tooth for the primer coat)
2. Prime with flat white enamel (dries quickly and requires far less color coat to develop a true color).
3. Paint with Model Master, Boyds paint, or something like Tamiya yelow.
If you initially paint very light dust coats, then build up to a full wet coat, chances are you'll get the results you want, with no paint lifting.
Also, if you find you don't like the paint job and want to start again, the thinners to remove the paint won't harm the plastic of your rare kit.
It works for me...............
Good Luck,
Lee Tree