This is probably the best advice so far. The OP stated that he couldn't even chamber a subsequent round without wiping the bore. That's a lube problem. Petroleum products shouldn't be anywhere near a black powder gun.
There are a lot of black powder competition shooters here (I'm not a competitive BPCR shooter), and they all have their own preferred lube recipes. You'll notice that none of them contain Vaseline.
I second the 50/50 beeswax and unsalted Crisco. I use it on all my black powder bullets. It keeps my revolvers running all day, and the last shot is as accurate as the first. At the very least, it'll give you a starting point.
There are a lot of black powder competition shooters here (I'm not a competitive BPCR shooter), and they all have their own preferred lube recipes. You'll notice that none of them contain Vaseline.