With the idea of learning from past mistakes, I am an expert at making mistakes.
Alumilite does not sell them, and I have not had one in years, but you can buy injectors for hand molding. Mike talks about the plastic syringe, and it works very well. Still, the problem with both is that the plastic cools inside and cleaning them out can be a real pain. A disposable syringe works best in my opinion, but sometimes you need to nuke it as well to keep it flowing. If you find a commercial molding injector, make sure it is one you can take apart to clean or you will get plugs and color transfer.
I had the hard plastic molds that were pre-made. I tossed them away years ago. I just love the RTV molds; they are just so versatile.
Like Mike, I use a larger batch. I prefer Pyrex measuring cups because they have quite a bit of mass to help hold the heat in. If you heat the plastisol, or Alumisol, in a microwave, mixing frequently, you almost can't burn or scorch the material. Heating small amounts in a hot pan will often damage it - not cool. Never use cast iron; it will transfer rust and change the color. I copper bottom pan would heat more evenly than an aluminum pan (my old mistake).
Mike suggests a single burner camping stove. I think that a hot plate would work well and they can be found a second hand stores or at box stores. Use this only to keep it warm, watch the temperature. I would suggest a candy type thermometer in the plastic and keep the plastic below the danger point. I think the temperature needs to stay around 350 degrees, but I would need to double check on it. I just pop mine in the microwave for a few seconds when I need to add heat.
I don't know what you use for a pour cup, but if you use a one cup Pyrex cooking measuring cup it has a pour spout on it. You can do a really good job on small projects. If you have your molds too close together, pour every other one then come back and pour the skipped ones. Still, gloves are not a bad idea until you get the hang of it.
Buy the way; I caught a 17-7/8 inch black crappie last year. For Washington State, that is HUGE. I did not weight it, and I did not take the girth, but it might have almost been our States Record. Be smarter then I was and keep a camera with you.
Big fish is relative. I remember working a small spring creek for an 8" cutthroat trout many years ago. That water was super clear and that fish was super shy. It took hours to catch, and release, that little fish. For that stream, the 8" was a trophy. Like I said, in my humble opinion, ‘Big’ fish is indeed relative.
Ericksat1, and you thought you were rambling - what about me?