There are two important pieces of information when dealing with resin: Pot life (how long you have to mix and pour the resin before it starts to set up), and cure time (how long you need to leave the resin in the mold).
I like resins with a longer pot life, but that tends to come with a longer cure time. Longer pot life lets you get a good mix and gives you time to work more air bubbles out of the mold. However, longer cure time means you can't make as many pours per day. So there's a balancing act you need to juggle.
Also, you need to have a way to very precisely mix your resin and hardener. Too little hardener and the cast might never set up (totaling the mold in the process), a little too much hardener shortens the working time dramatically, a lot too much hardener and you can have it catch on fire. If you can get a matched pumping set, that would be the best, second best is a balance scale but making one requires some math.
And shelf life is important since the cheapest way to get resin is in bulk and use a little at a time, but the pot life and cure (or demold) times will determine how easy the resin is to work with and how many models you get made per day. So I suggest starting with small orders of resin components until you find the one that works best for you.
Also, don't forget the gloves and a respirator rated for Volatile Organic Compounds (VOCs). Those chemicals are NOT good to be breathing, and you do NOT want them on your skin, either.
The resin itself should tell you what type of gloves to wear, probably nitrile. DO NOT WEAR LATEX GLOVES!!!! The chemicals in resins will go right through latex gloves, and can cause you to develop a latex allergy in the process.
Going to the hospital because your throat swelled shut from a latex glove is NOT fun.
