There are many ways of making the cartridges, as there were also back in the day. I found the system detailed on the capandball channel on Youtube to be excellent, and then I modified it for my own purposes, and to make it a little simpler. It results in a strong case that won't leak powder grains and is easy to load. Watch his first;
https://m.youtube.com/watch?list=PLI...&v=-2HUcfAyaaQ
and then mine;
https://m.youtube.com/watch?v=_JIyc6s8fnQ
The only part of the process that I'd consider challenging is making your rolling mandrel to fit your powder charge. I used a belt sander to make mine, though I suppose a lathe would be better. The specs given are for a 30 grain charge of black powder or an equal volume of a BP substitute. You want the ball or bullet to tighten up in the paper tube at the same time it tightens up against the powder. This isn't terribly demanding, as the perm paper will stretch to some degree. I find that my particular mandrel gives me cases that fit better with 32 grains of powder, and so you see that you can tweak both the mandrel taper and the powder charge to make things fit nicely.
Once you get the process down, it goes fairly quickly. I'll often sit down for a few minutes of a morning and crank out 10 to 20 cartridges, or just make up 30 to 50 paper cases for later loading. The powder measure you see me using (the Lee Perfect Powder Measure in this case) made things a lot faster, and also provides a much more consistent powder charge. There are powder measure though, and then are black powder measure. Apparently it's a safety issue, but Lee says that theirs is good "for all types of powder".
Search Youtube and you'll find a bunch of cartridge making videos.
All that being said, some guns take cartridges easily, and others seem to have been made to discourage the use of cartridges. Italian Colt repros are rather hostile to cartridge use, and you'd want to modify the loading cutout in the barrel. Original Colts took cartridges pretty well (it was the predominant loading method from the Civil War on) but for some reason the Italians can't be bothered with such details as correct shapes and contours.
Also, the Lee 200 grain conical (Lee mold # 450-200-1R) I use in my video won't load into most Pietta Remingtons unless you open up the loading cutout in the frame. Ubertis are much better that way, but the Pietta modification isn't difficult. You should be able to insert the bullet in a chamber and then rotate it under the loading plunger without any interference. Colts are a little more tricky with conicals, but look closely at photos of original guns and you'll see how they provide more room for loading than any of the repros. You can of course make round ball cartridges with my method, and those load more easily in an Italian repro, but repro Colts are often still a problem unless you fix the gun first. Let me know if you need more info on fixing a Colt repro so it will load like an original.
To my way of thinking, some up-front investment in time is well worth it for the benefits you reap in the field. During those long winter nights or periods of bad weather you can make up a lot of cartridges, or spend some time getting your guns to work right.