Well, joined the Geist club. Also picked up the 3+ kit.
So far just did a quick pass on a spot on the back seat - previous owner must have gotten some kind of ink or something on the rear seatback. There was an inch-and-a-half line that hadn't gone away when I did my initial cleaning after purchase (Tried Griot's odor removing leather cleaner. Didn't get that out, but very happy with it everywhere else).
Sprayed some of the cleaner into the provided brush, scrubbed in and allowed it to dwell. Took a few rounds, but all but a tiny spec of it out that's deep in the grain. Don't wanna risk marring the surface chasing it, so we'll call 98% a win.
The brush provided with the kit is a little more aggressive than my brain would go to for leather, but seems fine for seats. Don't think I'd use it on more delicate surfaces like a steering wheel or shifter.
Looking forward to working through the rest of the kit.