You live in country where bees have allways brood. It makes varroa control laborours.
Here is quite easy way to clean hive from mites. You may do it with aid of oxalic acud or without.http://www.xs4all.nl/~jtemp/dronemethod.html
Now first move the original hive to another place 10 feet.
Put onto original siten a new hive, 2 food combs and queen.
Half of bees fly to old site during 3 days.
1) You may now spray bees with oxalic acid solution frame by frame and you get rid off mites. You may use other stuff too like formic acid or thymol oil. You have one week time to kill mites which are on bees. The destroy is over 95%.
OA is effective and leave no trace in honey. Thymol gives awfull aroma to honey.
2) You may catch mites with larva comb. When hive has not larvae in capping age, you give a frame adult larvae and mites go into finished larvaes.
3) You have the hive with brood and mites. Again move it 10 feet and give new hivebox to old site. Clean mites away from bees. Hive has queen cells and give such one to new hive. When you have killed mites, joint that colony to the queen right part A.
4) It is better to handle mites with chemicals in the rest hive that they dont spread to nabour hives. Let workers hatch and again clean bees and join them into queen right hive.