Oh the water works, in fact it works so well it burst my Klein forks after only 2 hours in the cold.
Ouch that hurts so sorry that happened to you
All of these solutions seem a little extreme to me. As I understand with aluminum the problem with removing a dent, as with a bent tube or drop for that matter, is tensile strength. Steel has great tensile strength, it can be bent and straightened fairly easily, but aluminum tends to break. Hence the fill the dent and paint solution.
Agree with this completely.
Cold working aluminium will work harden it to a certain extent & this can lead to stress risers within the material.
Whatever caused the dent in the first place counts as cold working (the hardening may not be much at this point but could be enough to mean the dented section won't be the "path of least resistance" for the hydraulic/ice based methods) and getting said dent out with any of the methods on this thread also counts...
YMMV but personally I wouldn't trust a dented alu frame unless I was using it only in a low-stress environment.
============= Sig =============
Just a y2k FSR with some modern bits