You can't clean it the same way because the dirt is different.
The BP crud will get everywhere inside your shiny new pistol & furk it up from the inside out if you use the wrong techniques.
Now the good news.
The "hot soapy water" is the best thing ever & is
much easier than the regular cleaning stuff used for smokeless powders.
Get past the phobia, remove the wood grips, pull the cylinder & nipples & fling that puppy into a nice steaming bucket of hot water.
After cleaning shake as dry as possible & sit the whole ding-dang-doodle thing in a cardboard box & run a Wally-World $10.00 hair dryer in through the closed lid, flipping occasionally. When dry & hot oil with something that won't turn to road tar when firing BP next time.
PS: It scared the bejesus out of me the first time too, but now it's second nature.
Ball size depends on
individual pistol chamber diameter. If you get a thin, complete ring of lead wrapped round the rammer rod then you're good to go. If the ring is incomplete, go up a size. If the ring is wide & it is very hard to ram then go down a size. .451, .454 & .457 one of these will usually be right for your pistol. The balls you got sound a tad small, but if you get a complete ring then they aren't. You can measure the I.D. of the cylinder with a caliper to check before loading any BTW, Ideally you want a ball a couple of thou oversize from the measured internal diameter.