Trail's I've found to be more processor/calculator intensive.
What I would do is
I only know AS3)
1) make a movie clip of a small portion of the trial
2) have an on enter frame function that tracks the players(or asteroids) past and present position
3) have a timed function(I know in AS3 its possible donno about 2) that puts a new segment of the trail on screen. from the player(objects) privious positino to its present position.
No In this I've always used simple vectors so i could scale them if the player was moving REALLY fast, another solution might be to reduce the timed function to make it tick faster.
For asteroids I would just do a particle effect generator ontop/beneath the asteroid image.
so just an image of a piece of debris that is randomly scaled/rotated/directed behind the asteroid