Just getting into the crate in the vehicle is the 'turn on/it's time to train mode.
I always cue Karlo verbally on what we will be doing. The harness use to be the visual cue for protection, but we did away with it long ago.
When I go lay a track, I show him the articles and his reward toy(fox tail on a flirtpole) and ask him if he wants to find it. So he's already going into that mode while the track ages. Then when I get him out to track I put the fursaver on and tell him it's time to such.
Same for obedience, I tell him what we're doing while I put the collar on(fursaver or pinch)
Protection needs no cue, he's already heard the other dogs barking or the whip cracking and knows what's up. But I will now and then mix it up and just bring him out for another obedience session then put him back up.
His control during protection needed some work, and I found doing more ob will have him more readily what is asked before he's rewarded with bites.