Oh man, I feel your pain
Don't you wish we could put up a billboard? Sheesh!
One way you can test your gelcoat is by just putting water on it. If it sort of "runs away" then you have a contamination problem of some type. What you want is for it to just lie there in a big sheet (of water).
I don't know if the one big sheet of water means you are in the clear for sure, once it comes to paint
(I am not a professional painter); but I do know that the "running away" (where the water doesn't sheet but separates into separate pools) means the surface is not "clean" enough.
That's interesting info about the product you used. I, too, wonder how it did against the silicone oil/contamination.
I'm sorry you have had to tackle this problem
Lucky for your Scamp
to have you though