The catalyst that works with fiberglass resin, dangerous oxidizer if I remember correctly.
Grizz
Close, the catalyst is actually methyl ethyl ketone peroxide. That last "peroxide" is the difference between the solvent and the catalyst. This stuff is particularly nasty. Getting ANY of it directly into the eye needs INSTANT flushing with lots of water. If left for as little as 10 to 15 seconds permanent blindness is almost certain.
A paint store locally has MEK. I got some for special use knowing the risks. As a solvent goes it's simply not worth the risks to use on our firearms. Besides it evaporates so fast that unless you use lots of it the solvent will just evaporate away and leave the grunge still in place. Like water turns dirt into mud and then back to dirt when the water evaporates.
It's also not cheap.
If you're looking for a safer general cleaning solvent based recipe google for Ed's Red. It's easy and cheap to make up and highly effective. More importantly the ATF left behind in the spots you can't reach after the solvents evaporate will fight off corrosion and lubricate any moving parts.
I didn't bother with the lanolin they mention. And the odorless kerosene normally used for oil lamps isn't always around and isn't cheap when it is. So I came up with my own "close enough" version;
1/3 ATF, the red stuff
1/3 Varsol or "low odor paint thinner"
1/3 acetone or generic lacquer thinner.
I found that with the acetone if it is a grade with too much water in it that the final mixture comes out cloudy. Acetone, like alcohol, mixes with water. And the cheap acetone often has some water content which comes out when you mix it in with the other things. So I tend to use generic cheap lacquer thinner from the paint stores and get a lot less or no cloudiness in the final mixture.
For a little extra lubricity a shot of a good quality motor oil can give you a little more film strength. I mix my Ed's Red in a 1 liter paint tin I got from the paint store. To a 3/4 full tin I add roughly 1oz of Mobil 1 synthetic engine oil. I find this produces a noticeably more durable oil film that resists rubbing off on hands or being wiped off with a rag on the outsides of the guns. And the 3/4 full tin is nice for dunking parts without a lot of slopping around. But next time around I may go for a gallon can and make my mixture up so it's roughly 1/3 full.
Lots of fumes off this Ed's mix as well. Good ventilation is a must! ! ! ! I also strongly suggest good quality disposable nitrile gloves to avoid too much skin contact.