Do I need to clean/wash the microfiber towel after every use

You only need to wash the towel if it got soiled after you used it.

If you're applying to a really clean car, then you could probably get a few uses before you need to clean the towel.

If you are wanting to use other microfiber towels, just make sure to find something thicker. Our towels are really plush at 420 GSM, but you could get away with others that are around 350 GSM