I do and it's a hoot to shoot to say the least.
A couple of thing you need to know :
1- You cannot over charge with BP. The max charge is however you can cram in the case while still have space to seat a bullet. DO NOT leave an airspace between the charge and the bullet any more than a 1/16th of an inch. It can lead to problems like ringed chambers.
2- Before you do any loading, you need to determine your max OAL with the bullet you intend to use. An easy way to do this is to take a bullet, push it as far as it'll go in the chamber and then measure the depth from the breech to the bullet rear end with a calliper. This measurment plus the lenght of the bullet will yield your max OAL. Record this number. Now you need to determine where in the case the bullet will sit. If you'll be using a compression die, you need to determine where your final charge will sit in the case. To do this, take a case, substract you previous chamber measurement from the case lenght. Now you have a measurment of where your final charge plus whatever wadding need to be, taken from the case mouth.
3- A BP charge need to be compressed to burn well and produce constant velocity. Now that you have taken time to make a couple of chamber measurment, they will be easy to load up. Take you BP, fill the case until you are about 0.125" over the charge level you calculated earlier. Be sure to lightly tap the case to settle the charge or use a drop tube. This will be you powder charge. Weight it for repeatability and record it. Now you can do 1 of 2 things. Either put a cardboard wad in the case and then seat the bullet on top of it to your measured OAL or use a compression die to compress your charge before you seat the bullet. If you use a soft alloy, you would be better of using the later because it does take some force to compress the charge. If the charge is not compressed before you seat the bullet, the seating dies can deform the bullet. Either way you now have a completed round, Congratulations.
4- the search for accuracy will involve trying different powder weight, staying within the range where the charge is compressed and using different compression level with the same charge weight using thicker or thinner wadding to take up the space. Using Goex FFg, I found 0.150" work best. YMMV.
5- fouling control : BP is a very inefficient powder. It leave gobs of residue. It's no real problem if it stay soft. The lube you use will help you, containing vegetal oil to "wet" the fouling and prevent it from caking. Depending on the bullet design you use, you may have to use a lub cookie : 2 cardboard wads with lube trapped in between or a thick felt wad soaked with lube. If your bullet carry a lot of lube -read deep and wide lube groove- you could do without. You can also swab between shots or use a blow tube. A blow tube is a contraption made from a spent case and a 10-12 inch lenght of big vinyl fuel line tube. You basically breath down the barrel to wet the fouling and keep it soft.
6- spent case care : BP contain lots of sulfur and the fouling left inside the fired case will destroy them if it's not neutralised. When you get home, simply soak them in warm water with dish soap and scrub them with a small plastic brush to remove the big fouling.
7 Firearm care : As with the case, the firearm need to be cleaned ASAP so use the same solvant, water and soap. In the winter it may be hard to keep water from freezing so you can mix some rubbing alcool in the mix.
I have a H&R Buffalo classic and get group well under an inch at 50 Yds using peep sight loading using these process. Just dont expect lightning velocity from the old cartridge but with a 450 grain lee bullet, it's a real thumper.
That's a quick rundown of the process. If you have more question, I'll be more than happy to oblige.
Frank