If you can get your hands on some Devcon it is the best. Will not break down with solvents have tested shooters choice, hoppes #9, and a few others.
It is so stable that you can even machine it and hold tolerences. The Titanium Devcon is the best but you can use the Aluminum or Steel.
Here's the link Devcon
and here's the actual stuff you'll want to get Titanium Putty
I have used this on air craft parts for repair in crtical areas as well as leading edges of wings for dents. Used to use it a lot on B-One's and they can reach mach 1.7 so youll be more than safe for a long time going with Devcon products.
It's not cheap MSC has it and here's the link MSC Devcon putty