Take 1- 2 dl of bees from the brood nest and put them in a jar with a mesh lid on that is Small enough to keep the bees in and big enough so that the mites can fall out.
Take a few spoons of dry icing powder and put into the jar of bees and shake well so all the bees are covered in the icing sugar and are White.
After a few minutes shake the jar vigorously.
The sugar covered bees start to clean themselves, also it cogs the mites feet so they cant walk and grip on to the bees.
Shake the icing sugar into a fine mesh sieve, then wash the sugar away with water and you will bee left with the Varroa mite that were on the bees.
This method i also used to determen apistan resistance in mites : put some bees in a jar with a piece of apistan for 24hrs, shake out the dead mites Count them, then do the sugar treatment and Count the dead mite to determen if they are resistant to the apistan or other mite treatments.