This is something that I use all the time, and I am wondering if anyone else has tried it.
I made a stand with a shelf (the white plate) that is about the same height as the top of my lead pot, and an industrial electrical enclosure cooling fan mounted about 6" above it set to blow down. I use the fan to cool the mold as I am casting. I don't mess with the pot temperature, I just leave it set a little bit hotter than the "perfect" temperature for well filled yet frost free bullets. I use a ladle to fill the mold then move it over under the fan until the sprue goes solid. I then rotate the sprue plate by hand and drop the bullet out. If the bullets get frosty, I hold the empty mold under the fan for a few seconds. If the sprue freezes too fast, I skip the fan for a few casts.
The advantage that I gain is that I am able to cast faster because I am not constantly making small changes to the pot temperature and waiting for the lead to cool down or warm up "just a little". The fan cost $4 at an electrical salvage store and the rest was scrap I had tucked away in the basement.