I did some foundationless comb drone rearing last summer.
I wanted to have some extra drones for queen rearing as I am convinced there are no feral bees or kept hives within mating range and also wanted to pull capped brood to assess varroa mite levels and be able to destroy the concentration that should be mainly in drone brood.
A few things went astray from my plans. My bees showed me enough queen cells and forced enough splits that I never did get around to deliberately raising any queens. Whether from my own drones or not they create a few queens that laid well. Spring will tell how good they are.
None of the pulled drones showed a single mite. I neglected to examine empty cells for signs of mite feces which I could have been doing as well.
I pulled some complete capped frames and froze them and reinstalled for the bees to cart out the pupae but that creates a stinking mess in front of the hive. I uncapped and washed some frames out with water hose and tried air hose. Both methods a bit hard on the new comb and blowback messes up your glasses :
A few sugar shakes and sticky boards on screened bottoms showed only perhaps a couple of mites.
I found that hard to believe but I did do early spring Oxalic vaporization on all the original hives before splitting. These bees are considered to be mite resistant but the producer makes no public claims to that effect; Just that he only grafts from the queens that have wintered well, are gentle and produce well. I have noticed that they do groom each other vigorously on the landing boards.
It will take a few years close watching to see how they do as I back off on treating. Where my son is in Eastern Ontario having a high percentage of the same genetic bees, there is no way he can get away from high losses without keeping up the fight with mites. There are a lot of other bees in his area though. I may just be lucky on location.