Fix 66 Cuda fender

That looks a little deep to start with a hammer and dolly. I would pop it back out with a rubber mallet or ball of my hand from the inside first. Looks like it already has some hammer marks on it from the inside. I bought a hammer dolly set from pep boys for like $20 and it has 3 hammers and 4 dollies.
Although the hammers look similar, don't be fooled, you will have a shrinking hammer and an expanding hammer both of mine are round on one side and square on the other, the shrinking hammer will be flat on the front or slightly concave the expanding hammer will be more round on the face.

Ok so now onto the fun part. hammer that sucker, nope tap like you are trying to crack an egg without crushing it. Basically you want the metal to move but not with a single blow, many many many taps and you should see it start to get better, If you beat it, it will look like a sack of nuts (walnuts) when you are done. you should only be working on the high spots, after all low spots on the outside are high spots on the inside. Start at the highest point and work out from there, SLOWLY tapping around with the hammer. you'll notice I haven't said much about the dolly, well here it is, pick the dolly that has the closest contour of the panel you are working on, it wont be perfect but you should be able to maneuver the dolly to match the panel. there are tons of sites out there to help.
When you are done it should look almost shiny where you hammered it not pocked.

I would also suggest getting a piece of scrap and smashing it with a hammer and then trying to remove the dent. hammer/dolly work is a learned skill and I have a beat up fender to prove it, or I'm just a slow learner :lol:
hope that helps