a good way to do better at bullet is to premove the first few moves, but move pieces that protect your king and small movements. move pieces that are closer to each other.
Best bullet opening
Just play some random openings, and the opponent will think for a long time what to play and you'll win on time!
When playing bullet the best move is LONGER TIME CONTROL.
I am joking but to be your best at bullet adhere to opening principles as learned in the MCO and whatever coaching you have received. Don't hang pieces, all pieces protected, only move pieces once, like that stuff.
My personal advice is only use premoves for recapture or consider a premoves a gamble. Worst thing is when your opponent hangs their queen and your premoves is a lame pawn move. Ugghh
Good luck
Play the French openning