Help with glassing chemicals

I went to the supply shop and was given laminating resin, wax resin, mexp, and surface agent.
From what I understand the lam resin is catalyzed with mexp which would be used for ding repair and the lam coat.
I was thinking the wax resin and mexp would be my hot coat but I’m not sure what the surface agent is for if the wax resin is pre mixed.

Not sure why they gave you SA if you already have sanding resin (what you’re calling “wax resin”). The SA is added to lam resin so you can sand it. It is used for hot coats.
The sequence is this
Use lam resin (no SA/wax) to apply fiberglass as needed. Sand any high spots with coarse grit paper, after it hardens sufficiently. Add a coat of sanding resin, then sand smooth.
MEKP (catalyst) is used with both types of resin to create the chemical process of hardening the resin and changing it from a liquid state to a solid.

Oh, and one good reason to have SA on hand even if you already have sanding resin is that if you’re just going to one board and you eventually run out of sanding resin, you can add SA to the remaining lam resin as needed.

I use some extra SA in my sanding resin when I want to make some cheater gloss coat resin. The extra styrene makes it flow out a little better. I just do this on ding repair and wouldn’t gloss an entire board this way though.

Just to be clear: do you have wax resin or wax additive (often called sanding aid or SA)?

Also, not to be picky but it’s MEKP (not MEXP). At least, in english. I don’t know what it’s called in other languages.