It's called breech plug grease and has various brand names depending on the gun manufacturer. I think that TC's is called Gorilla Grease, and they often come packed in a small tube or tin. You can also coat the threads with Wonderlube or auto anti-sieze lubes, but they might not always be as compatible with shooting BP.
There's many effective BP solvents, here's 2 popular commercial BP solvents that have been highly recommended as being among the best:
Shooter's Choice Black Powder Gel
Butch's Black Powder Bore Shine, but be careful about getting it on your stock
Other include Birchwood Casey, Hoppes #9 Plus BP Solvent, Rusty Duck Black Off.
If you buy sabots and bullets in bulk packs, especially for practice, you can cut down the costs of shooting considerably. Just try to buy cheaper lead or FMJ bullets of the same weight and diameter as your favorite name brand sabot/bullet combo.
Experience helps to teach easier loading techniques. Having a small mallet and the right sabot loading accessories for your short starter or ramrod, marking your ramrod for proper bullet seating depth, and having an accessory palm saver type of handle for your ramrod, and/or a separate range rod dedicated to loading difficult projectiles, plus cleaning your barrel between shots all help to make loading tight sabots less difficult. Also having the rifle planted against a solid rest in a well supported upright position when loading is important so that you can lean on the ramrod and sabot with enough pressure to firmly seat it on top of the powder.