In those hard to reach places where you cant get in with paper to rough it up that is.

I'm going to paint a bike tank, and its got a fuel cap that flips open and cant be easily removed. I've tried a a small area and it hasnt reacted with the paint. The tank is covered in seams and little tabs for trim too...

Why don't you use chemical stripper? That's what I would do TBH

Then etch-prime.

[Edited on 20/1/13 by Daddylonglegs]

Nitromors? As long as it doesnt give any nasty reactions with the new paint...

I guess its all in the cleaning before painting then?

Its not mine so really dont want to screw it up

If its a paying job I would see if you can find someone close to soda blast it, quicker and cleaner and shouldn't damage any clips, you will then have the perfect surface for etch primer.
HTH