One simple way to kind of simulate threads is to do smaller chunks of the operatons in a timer. For example, instead of looping 10,000 times at once, loop 100 times in each timer iteration.
Ultimately, it will take longer time to loop through all those 10,000 objects but because it will not try to do it all at once you save some performance.
I have used this technique for large loops in flash and it has worked fine for me so far.