Here's a suggestion from Ronaldo Neep of Australia for full sized round balls.
: coat the balls with alox (Lee Liquid would work perfectly I suppose)
: a plastic wad, petals cut off, + wads (he used 2) to take up space
: insert the ball and roll crimp.

Sounds good to me. Now, the same system would work with a folded crimp as I apply.

The author also coated the inside of the case with alox both before and after loading the wads and ball. I am assuming this is the crimping area only as it would be impossible to lube the inside of the case after the shell is loaded. I fail to see any benefit to this, except the blast and wads would push more lube into the bore - it may be needed. I do know it is common to coat bullets twice when using Lee Liquid Alox.

The loads where developed for 12 bore 2 3/4" for round ball and for smokeless power, ie: Blue Dot and the system would work equally well in 20 bore.

He also experimented with a full sized 600gr. (12 bore) slug sitting on a plastic wad, petals cut off and attained 2" at 50 yards - I strongly suspect he is using a rifled tube - an H&R Tracker 11 to be specific.