Is it possible

There are some that are. We have a very successful mtt player, King Curtis, and if I am not mistaken he does not use any hud.
I do think that if you are multi tabling cash games, you would be better off using one.

Agree with the "one-of-a-kind" PooffyFooffy.

Playing one or two MTTs without a HUD, one may actually do better, but multi-tabling (cash, SnGs or MTTs), you are better off with a HUD (Or a BOT).

Obviously, we are speaking of "on-line" because using a HUD during a "live" tourney may be most difficult.

Maybe using a HUD can help you as a "teaching tool", but to be able to actually play good poker, one must simply do it themselves without the HUD crutch (building an internal HUD and confidence).

I don't use a HUD. Maybe I should, but I do ok when I concentrate and stay focused on the tournament (No more than 2 games at a time). I sort of consider a HUD to be a distraction from my "thinking" about the tournament itself and the other players play. I know I am likely wrong, but that is the way I view it.

Good luck either way!