I've met Garret
I was an extra on the show 'Deadwood' for almost two seasons, but more importantly, for ALL of season 2. As such, I talked with Garret a few times and got to watch him work. Heck, I even stood in for him one time (meaning, they used me for lighting and measuring distance and framing the shot, which would be a waste of the actor's time since he is likely memorizing lines, doing rehearsals, putting on wardrobe, getting makeup, etc.).
The first thing that amazed me was how prepared he always is. With the exception of one VERY hard speech he had to give, I don't think I ever noticed him blowing even one line. Ever. In fact, in discussions with other extras, I thought (until the speech that was really tough) he had to have a photographic memory. [in contrast one of the series regulars was notorious for blowing almost every line about a half dozen times each scene, and whenever we found out he was going to be in the scene, the extras use to look at each other in a silent overture of 'well, at least this means overtime', as it would often take 2-3 HOURS to do a scene if he was part of it (no I won't say who)].
The speech that gave Garret some difficulty was the one where he tries (and succeeds) to get get the heavy-set rich guy (who killed his brother) Mose mad at him, which subsequently got Mose shot three times in the stomach by Tolliver's guards (but lives). If you go back and listen to that speech, you'll see why it would be tough to deliver it.
He also liked to joke around. In the scene where they are trying to spread the rumor that the gold strikes will be confiscated by the government, I'm sitting behind Wolcott and Pharum on the boardwalk as they discuss LOUDLY the 'rumor' they are trying to spread. During this scene Garret would walk up to us between takes and giving us fake directions - 'ok in this take you will act like your mother just died'. I knew he was kidding, but the 2nd assistant director got a little mad at him for that (not mad-mad, but told him not to do it with a smile on her face... he is an actor and they treat them very nice... hehe).
He use play catch with a baseball on the set with people on the set.
The only other story I have is that I don't think it was suppose to die at the end of season 2 until the last moment. As such, his mood seemed to change while filming the last episode; a bit melancholy. Plus, they had built a life sized doll to be hanged in his place, and it must have been eerie to see 'yourself' as a doll and hanged! These dolls are AMAZINGLY lifelike, I actually was startled when I first saw it (the prop guys played a joke on us extras by putting the doll in a chair next to where we had to check out at the end of the day, and until you got up to it you wondered why Garret was just sitting there motionless!).
Anyway, he seems like a very nice man. He is proving to be an excellent actor, and it's cool I got to watch him work (for more hours than I care to admit)...