I prefer WD-40 to remove cosmoline....
It is somewhat flammable, but I take it and just spray it down and let it set for while...(penetrate)...and then wipe off what has turned soft with little effort.
Then repeat a few times as nescessary! It really works very well!
You could completely emerse an action in it and leave it..all cosmoline would just melt right off.
And there would be no reason you could not put it in your parts washer. They sell it in 5 gallon cans to 55 gallon drums.
And my parts washer has a fire safety that drops the lid to snuff out fire in the case that it happens.
Most everything thats been in my parts washer has always been flammable.
i.e. varsol, wd40, diesel...
I have also used Mean Green and Purple Power in them for a non flammable option but would not reccommend for cleaning firearms!
You could if you went from cleaner to a complete air dry down and oil application but Purple Power is acidic and could damage some finishes.
I used diesel one time in it but didnt like it much, and never would use gasoline to clean with....dont like it at all! ( except to run my truck )
Just found this non flammable choice on internet...
http://www.shooters-choice.com/aqua_clean_action.html
Aqua Clean...Know nothing about it...looks good! and they like it! $62.99 a gallon!
Might find better deal by shopping around... I might try it though! Usually get what you pay for MO.
And here may be another option:
http://www.aircraftspruce.com/catalog/cspages/lpst91.php
Not familiar with it but LPS makes good stuff