Sir, the whole point about the Minie bullet is that it was designed NOT to be patched - it was designed to be an easy, accurate and very fast load by comparison with the predecessor patched ball.
Patching per se is either for RB [round ball] or for the later elongated target bullets in the 1850-1880 era shot from Rigby and similar match rifles of the day here in UK/Ireland and the USA/Canada, and for the wide range of continental Schuetzen-style rifles in Europe and the USA. In the USA in particular, the sport of heavy 'slug-gun' shooting is still immensely popular, with remarkable accuracy being achieved from two-piece bullets and cruciform patches....
Sorry, I digress.
As for filling up the base, well, go right on ahead, if it pleases you. It really makes no difference whatsoever, except using up the stuff. And [BTW, what do YOU use?
You have hit the main point of all this firmly on the head - '..enjoying it' and '...finding it very therapeutic', and THAT, my friend, is what it's all about.
Best graders
tac