You will find as you get more proficient that the molds will get too hot. You can regulate your mold temperature by adding more molds as your session progresses. A few years ago I was doing a lot of casting, all by hand. Starting with one mold, as it got on the hot side of what I liked, I added another mold. Usually I would end with either 3 or 4 molds running in succession. If I was using both aluminum and steel molds, then I had to set up a rhythm as the different metals dissipate heat at different rates. It took a while, but I soon learned which ones to use and when to maintain their temperatures. Having the bullets mixed was not a problem as I sorted when I inspected, and at the time I was using straight wheel weights for all my casting needs. It is a blast and some satisfying to watch an animal being harvested with 'one of my own'. The big guys make great bullets and we've depended on them for years, but since I've started hunting with my flying wheel weights, I use other types of bullets less and less.
Regards,
Sweetwater