Been enjoying more tastings lately and don't believe this issue as been brought up before and it's something I have encountered that has a quick and easy fix.
Wash your hands before tasting!
This ensures a tasting glass that doesn't get dirtied up with fingerprints on the outside. With a clean glass that stays relatively clean during tastings you can enjoy more the legs and color of a whisky. Had a tasting at the shop the other day and my tasting glass looked like it was ready to be sent off to the crime lab with 100's of pristine finger prints.
ps - don't use a heavy perfume or floral smelling soap either. If this is the wife put all around the house try baking soda and warm water.