John Boy, thanks for that link on the cleaning fluid.  I ordered a sample and it came in today.  (Wow that was fast!)  Next time I cast, I'll clean my mold with it and see if I get any improvement.

Nice Article:
How to cast bullets and other tidbits ..
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Back to web access here and I read the article. I agree with  him, but a couple comments. 

Be very careful touching wax to the sprue plate pin.  It is easy to contaminated the underside of the plate and even the mold cavity. Hopefully, if it happens you can burn it out with a match or candle.

Super hot for pure lead works but, I was able to cast a batch hollow .54 round balls at 900 + degrees.  I started just using 50:1 lead tin mix.  It doesn't take much tin to make lead flow better and the RBs do not notice a smidgen of tin.

Water near molten lead?  Not me.  If you ever empty a 20# pot with a drop of water, you will never forget it! 

Timing is everything to maintain mold temp for sure.  That is where the thermocouple on the mold pays off.  I finally figured out, after many years of weighting, ect., my bullet weight variations were in the mold temp variations caused by casting rate, stopping to flux, ect and not having any way to know when my mold was at the proper temp.

Quite frankly it is a PIA until you get used to it.  I drilled and tapped a lower right front corner for 8-32.  I run the wire along the handles to the meter.  It is about 3 feet long.  Any shorter would limit movement too much. 

I cast another 100 tonight.  I noticed a little buildup on the base plate.  Cleaned and smoked the mold. I watched the temp a little closer too.  Culls that were more than 5 degrees of target temp varied from 213.2 to 213.8 grs.  After cleaning the mold 65 bullets averaged 213.37 grs.  after I stopped for a few minutes I had 3 in a row that weighed 213.6.  I had one odd ball that weighed .8 and the lightest were 2 - .2s.  Of the 65 after cleaning the mold 50 of the 65 weighed .3 or .4.   No doubt with a little more practice and watching the mold temp tolerance a little tighter,  a +/- .1 to .15 tolerance could be held on 98% of the bullets cast. 

I am curious about adding a dimmer to the pot to maintain exact temp without any cycling of the stat. Before, I felt the tolerance with mold temp sensor was so tight, it didn't matter.  It probably doesn't on the target.  I couldn't tell my culls from good bullets a few years ago on the target when I was shooting regularly between matches.

Note, as the mold cools, sometimes it will hold at 5 degrees above for a few seconds, start dropping and be at temp or a degree or two below by the time you get a bullet poured.  I try to anticipate and get them poured a degree or 2 above target temp, 415 tonight. Once in a while it will shoot past cooling.  If it gets more than 5 degrees low, cull them. Culling anything below will probably tighten up the couple that were .3 or .4 off the average. 10 degrees low definitely gets off .5 or more.  

How good is good enuf and how much effort is it worth to make them all +/- .0 grs? 

The interesting thing about watching mold temp is sometimes you have a wait a bit for the mold to cool and at times it is hard to keep up.  I certainly understand now why my bullets were varying over a range of +/- a whole grain before I started using the temp sensor.