Sort of. If you're adding media from another tank, you're not really cycling per se. You're merely bringing in appropriate bacteria necessary for handling the nitrogen-based products. Which means you may not have to do anymore to the tank at all, depending on the bioload that you introduce (and even then you could experience a slight ammonia spike). Typically, a pure fishless cycle will involve adding ammonia to the tank. However, including used media during the process can drastically speed things up, especially if you're wanting to load up the tank quickly with fish.
What exactly do you mean by you "dropped in an old filter from my 75g"? What did you drop in? What kind of fiter do you have on the 29g? The time between adding used media to a new tank and adding fish is not really the question. IMO, it's more of a question of how much used media has been added and whether it's enough to handle the bioload immediately.
I think you're on the right track by putting in used media and there just may be enough in there to support the fish you're planning.
