You can also use Vaseline. Some guys use Olive Oil, but I've always had better accuracy with Vaseline.

I used my 60:40 BW:Vas mix on REAL grooved bullets in my .45 cal. longrifle.

I was able to fire 10 consecutive shots, shot after shot, no wiping and grouping under 1 1/2" at 50 yards, then go right back to shooting patched round balls without any wiping needed.

The BW:Vas worked just as well in my longrifle, as-did the same mix in my Rolling Block with .50 cal. 550gr. bullets.