How can I minimize the number of merchants for given set of requested bricks? This question should be answered in Bricklink FAQ, but I didn't find answer there.

I'm a casual Lego hobbyist, I have a few sets with random pieces missing, about two dozens of them. Some are truly rare. What is the best way to find smallest group of sellers having (collectively) all required bricks? It will minimize cost of sending packages overseas.
You can create a wishlist, then view sellers ordered by the number of lots they have of the items in that wishlist.  That should give you a good starting point.