"..every so often I'd get a glob of lube under a bullet and would have to clean it out. Was this because I didn't use a heater on the sizer?"
No, that was caused by not pulling the lever down hard enough to prevent lube seeping under the base when you tried too hard to completely fill the lube grooves 100% (which really isn't needed or helpful).
You can get an idea of how much bullet lube you're using by firing several rounds and looking at the muzzle - excess lube will make a greasy 'star burst' at the exit. When you have the 'right' amount of lube the star will be clear but not heavy.
I love the performance of NRA formula 50:50 Alox/beeswax in my old Lyman 45 but I've not tried Lee's version - yet.
