Sometimes 2, most commonly 3, sometimes 4 for a session with more accomplished, very rarely 5 for finishing something up. I briefly intended once to award 1 xp per scene/encounter a character contributed to, but dropped that just about immediately when I saw a good player hang back to let someone else have their day in the sun. And I never liked xp for playing up disads, since it's too easy in a long game to have them be a net positive xp farm. So I really just awarded the same to all players present.*
Indirect factors - we had some time skips sometimes, and that to me helps explain characters growing more powerful in the setting, even if the mechanics are xp for game sessions.
Also it helped that I asked for, and mostly got, well-rounded starting characters (ideally any samurai should have a game or perform skill, a lore skill, and a social skill), plus spending xp on things related to what they were doing, or seek out some kind of instruction. In that context I didn't mind people spending xp on the spot when it made sense; it was equally common for them to save up for something anyway. (Also these relatively unoptimized characters tamed the power curve just slightly, so we didn't have as many glass cannons walking around, which made my job easier.)
*Absent players/characters got nothing directly, but sometimes I awarded extra xp specifically for certain things. Maybe lore skills, or Allies, or something. Sometimes in time skips, but also a character doing their own thing off camera while their player was gone might still get something, but not necessarily combat skills.
On training, I meant to require returning to dojo for technique, but it varied by game and whether down time made sense. An "aha" moment or sudden enlightenment where finally the technique makes sense can fit the setting, but I still like it to come after some training or meditation rather than literally in between rooms somewhere.