Dave Millers method works very well. As an alternative to the hardwood drift I use a toothbrush handle with the head cut off. The threads form grooves on the end of the handle which then grip the threads of the filter ring.
The key to success is not to beat it into submission with one or two whacks, but persuade it to return to shape by a series of taps.
Micro tools also sells a hardwood anvil which the lens is rested into so you don't overshoot the target.
The anvil is a hardwood blank with a series of different size notches cut into it. Think in terms of a 2" hole cut in half. Vary the size to suit.
Also the lens barrel is often hardened aluminum & doesn't take to being flexed. With the ring bent it probably is cracked already so be careful.