Release agent from the manufacturer was going to be my guess, or armor-all overspray if it was an older model. Scuff everything up real good with a scotch-brite pad or sandpaper (not too coarse-maybe 400 grit) and wipe it down with whatever thinner is compatible with your paint/primer. Allow it plenty of time to dry and then hit it with your primer. The primer should seal everything up with 1 or 2 coats and you should be able to get your paint to go on without any fisheyes. You can do it without primer but you'll probably have to shoot a coat of paint, let it dry, scuff it with scotch-brite and shoot again until it lays down smooth.