I've used a gooey/wet bear-grease or marmot oil patch for hunting and experienced no problems with migration of the oil/grease. That is, I noticed no extra fouling when reloading and no change of the point of impact.
Nowadays and for many years, for a hunting lube, I use either Neetsfoot oil, patch wet, or Track's Mink Oil, patch soaked then squeezed out slightly. Same results at with the bear grease and marmot oil.
For the December primitive moose hunt, I ended up with Mink Oil lubed patch for the first shot, with a card wad between the patched ball and powder as I thought there might be lube migration. Subsequent shots were paper ctgs from my pocket. In effect, the first load of patch ball was not necessary, as the paper ctgs. hit the same poi and gave the same accuracy. In my .69, this barrier wad did not effect the POI, however, if other rifles, the use of a wad changed the POI- so- one MUST check this before hand. If wanting to use the wad, make sure you test it first. Without a wad and using Neetsfoot Oil as lube, my rifle has been loaded for up to 3 months, yet when discharged, no hesitation and the ball striking as it should. I immediately reloaded and No Problems experienced.
So- if you want a barrier, just because, have at it, merely check to ensure the point of impact or accuracy does not change.