The cigarette papers (American Spirits) worked very well for me, but would leave a small piece of paper residue in a chamber or three each time. I wondered if it would become a problem if I left them, and fired 3 cylinders without removing any and had no problems. I'm not sure how long you could go or if it would cause any problems.
Nitrating those papers just wasn't so much fun anymore, and was a little messy with crystals falling off when you worked with them.
I have never greased over the chambers. It's a bit messy, but it's hot in TX and it might just end up dripping or coming off under recoil. Some people do though, and it works.
I often shot without any lube with balls, but if I did lube it was with home punched wads soaked in Gatofeo's #1 lube. Great stuff which I also use as conical lube.
My father gave me an inline capper when he gave me my Old Army, but it gave me problems so I just cap by hand.
I've heard a lot of praise for the Ted Cash snail capper, but many Remington 1858's seem to have smaller openings and just don't fit well, though I've also read of someone modifying their capper to work.
With a brass frame I've read 25 grns is about the absolute max you'd want to load in it to keep it from battering the recoil shield and opening up the cylinder gap.
Many people use Cream of Wheat as filler. My father gave me a bottle of it too, and I've used it, but I grew tired of measuring another thing, especially in the wind. That's what I use wads for, which are easy to use and the same each load.
You certainly add the filler between the powder and projectile. Don't mix it with the powder.
When I've had a chamber fail to fire it's been because the cap was missing the priming compound inside. Recap and shoot, unless it's contaminated powder or a nipple channel that was plugged. You'll want a nipple pick, which is the easier things to try first.
If you do have a fail to fire continue to point down range as there could possibly be a hang fire as well. Give it a while before you mess with it.
To unload a loaded chamber you can try pulling the projectile with a ball puller. There's also a CO2 discharger tool which attaches to the back end and quickly pressurizes it like a pellet gun to dislodge it.
I greatly enjoyed making paper cartridges and still have plenty of packs of papers still.