Actually I used the "dot on the wall" technique to black out my vision in the situation from the OP, though I couldn't keep it up, I was still able to see them with my eyes open.

Are you able to use this technique in a lit room? Cuz it was hard for me even with all the lights off (except some light coming in from under the door).

I think I will use that technique to practice getting into Hypnagogia faster, and hopefully use that to manage the HIT again.