All of the above is good, I have mostly Snap On body hammers. Years ago I bought Harbor Freight body hammers and dollies. I still have the dollies, after reshaping and polishing them. The hammers are soft, mine were yellow handled, and the handles were made of steel - sucked using them.
Lots of dollies, the more the better. Find a piece of railroad tie. Lots of blocks. Lots. From big to small. My longest block is a custom aluminum 5' block. Smallest is a "Nib block", but I use it with paper.
No one block will block everything... blocking is the key to a flat panel and high quality paintjob. A trick I use (learned it from an old bodyguy) for odd, intricate panels is to use a contour gauge to measure the tricky area, transfer the pattern to a block, and cut the shape out with a bandsaw. If you use a "donor block", then it is ready to go. You can use wood, plastic or whatever, but glue some kind of interface on the block, so there's no digging into the panel... This is the best bang for the buck you will get - custom blocks.