Don't worry too much about that striker channel. It's fine to clean it once in awhile but not generally a big issue after each shooting session.
It should be left dry. If your talking about squirting some brake cleaner in there to flush it out, that's fine. I don't even do that every time, in fact I seldom do.
Don't lose any sleep over instructor comments neither. They have a natural tendency to put down things they don't understand.
I think it would be best to get a bunch of rounds shot and get the gun running well before any class's.
In Memory of Paul "Dietrich" Stines.
Dad: Say something nice to your cousin Shirley
Dietrich: For a fat girl you sure don't sweat much.
Cue sound of Head slap.
RIP Muggsy & TMan
"If you are a warrior legally authorized to carry a weapon and you step outside without that weapon, then you become a sheep, pretending that JOCKO will not come today."