If the OP really has twenty colonies or more, I personally would of thought an Api-melter would be a worthwhile investment.
They are expensive for what is just a heated stainless box, but neither the TA nor my insurance provider would entertain a home built appliance.
Whichever brand is chosen, they are so useful, and with prices continuing to increase, doesn't make sense not too.
Our three cost just over five grand, bought over a few years, just one is now nearly four grand.
As it seems I'm allowed to mention Abelo, the premium model we have just about sorts out all shortcomings of both Lyson Pro and swienty.