I didn't bother with the early May or Roxanne battles as I didn't have Mash at that stage, but I got the main ones after that. Brawly wasn't so hard cause I got a lucky critical against Machop, and then Mud Slapped Makuhita so he couldn't hit with any fighting attacks. The strategy with Wattson was very similar, I Mud Slapped so that he couldn't paralyze Mash, cause that made it much easier for Magneton to hit him. Maxie was a piece of cake other than his Camerupt getting a Magnitude 9 while Mash was underground, almost getting a OHKO, but he survived and got that KO he deserved.
Torkoal was the only problem in the entire gym as I ran out of Digs and had to resort to Metal Claw, but Torkoal managed to get two Overheats in, almost KOing Mash, but he stayed strong. May's team got OHKO'd other than the Wailmer as always, but other than that, she was easy. Winona's Altaria hit for a LOT of damage with her Dragon Dances, but a few Secret Powers put it out of its misery. I finished up there at lv48 and as I said before, I'm really happy with my progress.