Damn, it never occurred to me that you'd have to use that spinning in air technique so much to maximize the score.
It's one of the key features of the gameplay that makes it so much fun and was so disappointing in the sequels when it was capped too low.
Anyway, the most efficient way to max out your score is in this forum's high score thread. Just get beneath a bird in the bouncy cloud area, let the game bounce you into it until it stops giving poits, grab the 1up and jump in a pit to your death. Repeat.