You've gotten good feedback here.  We use either a molasses based liquid containing Rumensin, or we use a 1/2# pellet that contains just the mineral and the Rumensin.  Remember, for cows the legal feeding level of Rumensin is 200 mg/hd/day.  If your supplement is 400 grams Rumensin per ton you can feed 1# per cow per day, if your supplement is 500 grams Rumensin per ton you feed .8# of Rumensin.  Also realize that most supplements should also be carrying mineral and may very well provide all the mineral that you need, so you can probably save on the free choice mineral when force feeding the pellets.