I use open barrel feeding and to medicate with Fumidil B, I plan on dusting. 
Here is the recipe from a reliable source who would prefer to remain 
nameless due to liability issues as they are closely associated to 
production of the product.

one bottle 9.5 gram Fumidil B
one lb soya flour
13 lbs icing sugar

For fall medication...3/4 cup per colony for proper dosage.  I use a wax 
paper roll cut on a chop saw in two inch strips to hold that quantity of mix 
on the ends of top bars.  The soya flour is for preventing clumping.

Any concerns with this method??

Claude Hachey
New Brunswick, Canada 

******************************************************
* Full guidelines for BEE-L posting are at:          *
* http://www.honeybeeworld.com/bee-l/guidelines.htm  *
******************************************************