I have good luck using Devcon 2 Ton Epoxy.
1. It has a 30 minute working time that lets you get even the most stubborn broadheads aligned.
2. It has a working temperature of -60 to 200 degrees. You can later remove the broadheads with a torch without going nuclear!
3. It is water proof.
4. It is recommended for both wood and metal.
Like the others have said, it is best to clean both the adapters and the inside of the broadhead. I have a wire strung across the front of a workbench that I have clothes pins clipped to. After I get the broadheads aligned I just hang the arrow by the nock until epoxy dries (about two hours). That way I have not changed the alignment of the broadhead, which may happen if you lay the arrow on a bench or lean it up against a wall.
Below is a picture of a jig I use to align the broadheads. Pretty simple but it works great. I can usually get the broadheads aligned within .003-.005 inch, which is a heck of a lot more accurate than spinning them on a bench.
Good luck!
Goose