You would need to melt the existing lube out of the grooves. Boiling the bullets in a pot of water works great for this.
Crisco alone is too thin, with too low a melting point.
Melt a 50/50 mix of Crisco and Beeswax in a shallow pan over low heat. This is not a precise mix, but a simple TLAR process. (That Looks About Right) It should be deep enough that when you place a bullet in it base down the groove is covered. Place as many bullets in the lube as you can, maintaining a 1/4" clearance around each.
When the lube is just solid, still warm, use a fired .45 Colt case with a roofing nail stuck thru the drilled out primer hole to cut out the bullets from the lube cake. Refill the holes with bullets and repeat.
For a few quickie loads if desired, simply load the bullets with their current smokeless lube, then when loading prior to going on the line, put a glop of crisco on the nose of the first round to be fired. One of these per cylinder full should get you by. A squeeze tube of Bore Butter from a shop selling Muzzle loader supplys works even better for this.