Over the years I've heard lots of shooters comment that they're interested in trying black powder loaded ammo but a very reluctant to actually have a go because of the clean up "issue". Some are terrified of causing corrosion and others have heard that it's a horrendous amount of work - usually from people that have never done it themselves. It's really not hard at all and I'll go into how to make it easier.
Black powder fouling is nothing more than soot. Lots and lots of soot! About half the powder volume is turned into soot and most of blows out the barrel each shot and can be seen in low light as that beautiful blast of orange sparks and delicious white smoke.
To illustrate how much soot there is, In a muzzle loader for instance, incorrectly managed fouling build up is so rapid that in as little as four shots reloading becomes nigh on impossible. There are ways to manage and reduce the fouling build up in both muzzle loaders and cartridge rifles till it's no longer a problem at all. It mainly comes down to understanding bullet lubes and what they have to do and just plain water.
Black powder fouling is water soluble. You don't need any shop bought cleaning products. You just need water with some detergent in it and regular cleaning patches albeit many more of them.
Fouling management is also one of the functions of an effective bullet or round ball patch lube and I'll mention them separately.
In patched round ball muzzle loaders grease lubed patches are useful for hunting as you'll only fire a few shots at most but as few as four shots and grease lube patches fail to keep the fouling soft. For range shooting and plinking wet patch lubes are unbeatable. There are lots of versions and they all work pretty much as well as each other.
The brew I've settled on is 430 ml water, 60 ml soluble oil (cutting oil), 30 ml liquid soap (eg. wool wash) soak your patches and lightly squeeze them out and using almost dripping wet. The 60th shot is as easy to load as first as each reload wipes the barrel. This brew is also an excellent general purpose BP clean up product.
Cartridge rifles are a little more involved. Aside from providing bullet lubrication, their lubes have to chemically combine with soot and promote moisture absorption to keep the fouling soft. Most BP cartridge lubes are beeswax based and there are as many recipes as their are shooters. Other typical lube recipe ingredients are olive oil, neatsfoot oil, parafin wax. various animal fats (lard) and some have tried engine oil as an ingredient too. Some learned sages say that if you couldnt eat the lube your rifle shouldn't either.
Not all lubes behave the same in all rifles. A lube that's works well in one barrel/bullet/powder combination wont necessarily work in another. Some bullets cant carry enough lube to make it the whole length of the barrel. You can tell if it does or not by looking at the crown of a clean barrel. You should see a star shaped splatter of goo on the crown if there's enough lube.
Humidity also plays a part in keeping the soot soft. You can provide more by blow tubing. Moisture in your breathe will be absorbed by the soot to keep it soft. I hate blow tubing and use it sparingly. In my Sharps .40-65 I can go 40 shots without blow tubing or putting a cleaning rod down the barrel and still have it clean with 6 patches at the end of the day.
I've only briefly covered the black art so far but will try help with answers and info if you're interested. I'm sure other BP shooters here will dive in and help too.