The spackle I use is available from any hardware/building supply store. There are a variety of brands. I am currently using Home Hardware's brand. They call it wall repair compound.

I have not had any problems with it not sticking. There is not much left on the wing anyway. Most of it is sanded off. Of course it cannot be wet sanded. I use automotive primer to paint my aircraft and there is no ill affect. Once the primer is on I can then wet sand.

Ed S