Good idea on bell curve for culling boolits......
Are you having any issues with the bases of the Mihec boolits? Getting a clean base and square gas check has gave me fits, most bases are a tad over sized for the check.
As far as lubes go, I'm running White Label BAC and Carnuba Red in a RCBS lube/sizer. Being in Florida our temps routinely run between 70 - 80 degrees this time of year, I haven't seen any wax issues. No leading issues either with WW's air and water quenched. I've not tried to add a harder alloy, yet.
Not a problem with Hornady Gas Checks. In fact, prior to sizing thru my Lyman 450, some of the checks were a bit loose.
I did however use "old" gas checks:

I also have a box of "old" Sierra gas checks.
When they run out, I'll be making my own. I have a "Checkmaker" idling on my shelf.