Totodile dances around.
Heck, I completely forgot Noctowl even lived at Oak's.
Muk jumps on Oak/Tracey.
Honestly, Bulbasaur is pretty much the only one I think trains, due to his protecting the lab and what-not. The reason they come back so strong is just so the writers have an excuse to have Ash pull off a win. I mean, really? Torkoal wasn't a horrible Pokemon, but for it to stay at Oak's after a terrible record at the Hoenn League and suddenly come back and nearly beat a Frontier Brain's Legendary... He honestly did not train that hard at Oak's. Just an excuse, imo.
What would Sceptile do I wonder?
Oak's ranch hasn't got that sort of jungle-like environment, and there aren't many rival Pokemon he would be sparring with, unless we see random trainer's Pokemon like Kabutops or Aggron somewhere...
As for Totodile, he does what he always has, dance!
Snorlax naps, and EATS! I guess he's one of those Pokemon who are like "I'm bulking up for Football! (American, not Soccer)"
Bayleef, not entirely sure about her, I can't even remember what she was doing in that Chronicles episode.
Corphish is the only one really that I can see training, I'd say he spars with Kingler and Gary's Krabby.
Yeah, Bulbasaur's the designated leader of the ENTIRE ranch, so I'm sure calming down the Tauros herd and maybe some rampaging Nidoking/Kangaskan/whathaveyou is enough.