if it's a true .75 smoothie, i'd suggest some testing for a good ball diameter first, and that will depend on whether the ball is naked or wrapped. i think yer mention of a .765 ball was a typo. also, personally, i'd rather wrap a ball in well lubed cloth, which will mean a much smaller ball diameter and a much tighter barrel fit than a naked ball. a well lubed patch allows me consecutive loads without addressing fouling control and offers a better gas check. i use a .590 or .595 ball w/.015 greased patch in a .62 (which, like most .62's is actually .615).
however, to be historically correct and emulate the 18th century fowler (if need be), tow was a favorite for loading ball or shot. cloth was a premium and used for where it counted most - clothing. wasp/bee nesting, leaves, mulch, balled dried grass, leather, paper - all were used for wadding.
as to loading shot, lotta variables that will require testing in yer gun. the basics usually work at least ok - powder load, shot card, lubed shot cushion, shot load, over shot card wad.
lots of good ways to load a smoothie for ball, buck or bird shot. more posts from others will show that .... but what yer gun wants might be diff'rent.