I would expect you want the finished size of the bullet after patching and sizing, to be at most, .001" larger than the bore, just so you can load it.
I did OK with using commercial, grooved lubricated bullets in a .50 cal barrel that were only engraving on the top band. I had with .008" deep rifling,
but better with a oversized, groove lubricated bullet that was pushed through a section of the barrel to impart rifling on it's periphery.
I did not experiment with paper patched bullets as I did not want to have to wipe or clean the barrel between shots. This barrel, with the pre-engraved
bullets used to shoot MOA at 100 yards, using very cheap aperture sight rear and globed post on the front. I would not have to wipe the bore until
all shooting was done for the day - then it was cleaned properly.
There are .366" groove lubricated bullet moulds on the market already. Of course, moulds are not inexpensive & I can see the desire to do it right, the first time.
There are also .360" paper patched moulds, which I assume are made for that or similar "sized barrels. eg: buffalo arms
In retrospect, if your rifling is only .002" per side, that is rather fine. Taylor had a gun with only .0015" deep rifling and a bore sized, paper patched pure lead bullet gave him
1 1/2" at 100 meters.