Originally Posted by Alpha67
Thanks guys - I knew the sanding of the exterior surface was a must - was wondering if I could avoid sanding the nooks and cranny's of the inside of the fender though (will be visible/exposed on the engine compartment side
Unfortunately with body prep there is no easy way out, that's why not everyone enjoys it. You do have to scotch brite all the surfaces in order for whatever you put on top of it to stock to it.
I would use maroon scotch brite (320 grit) pad and then give it 1-2 coats of epoxy (I use SPI) and wet sand that with 400-600 and you're ready for paint.
Here's some pics of fenders I did for a guy with the above process.