NICE or DRICE? I'm going to attempt to make a cryogenic engine, like the centaur on the atlas V
Also, how would I keep MWAX in its molten form at the standard temperature also for rocket engine uses
You will need to have adequate insulation to keep those elements cold, same thing with MWAX...cover the interior of the fuel tank with INSL is a good start.
Anything else?
Shoot electrons into deut to cool something down. See