Help! Epoxy is coming off...

[Guus]

I spent ages removing the old paint from my P5b... Finally I got it all clean, I used extra rough sanding paper on the last turn to create a good basis for the epoxy. Then I used degreaser from hammerite for a clean and then applied three layers of epoxy. It looked good! But when sanding down the plaster it came off without any trouble!!!
What did I do wrong and what do you use as grounding (I'm afraid I can can get all the epoxy off again...)

Thanks in advance!

Best regards,
Guus

[Phil Nottingham]

Expoxy filler will normally stick like glue to any non-gresay steel soothe or rough and even rusty. The hammerite degreaser must have left a residue?