The paint on my petrol cap is in a bad way with lots of cracks and flaking.

What can I use to take it back to bare plastic without destroying the cap?

And can I use chopped fibreglass to fill in the back of the cap so I can then redrill it for a different, larger, lock barrel? If not, what would you recommend?

 

I've used JB Weld in the back of the cap, and may need to add a little more, but I used all I had.

It needs 24 hours to fully set so I'll post the outcome.

Any suggestions on the paint removal?

 

Without seeing it it's hard to say , but id guess if it was mine id sand it down with a 180g disc , then 2 pack prime it , flat that down before top coating