Keeping microfiber towels dedicated to one task or product is the key to extending their life expectancy and usefulness. The other is washing them separately as well.
if you cannot do this, at least try to wash them by hand with a good APC before throwing them together in a washing machine. Washing three of four separate "loads" of two or three microfibers used for one specific purpose does not seem economical or efficient to the non-ODC-type person, but it's that the reason why you are trying to prevent cross-contamination in the first place. Why use the same towel to apply plastic protectant and then use it after it's been washed to remove a wax or sealant? Hard to explain that to the uninformed "detailer" who wonders why their wax-job looks streaked or smeary after they wipe it off!!
Sometimes it looks crazy to have soooo many microfiber towels, and yes, it can be expensive to have and maintain such a "collection". But if you want your vehicle to look like the pro's who post their car-art/workmanship in this forum, you will need follow suite and imitate this detailing step. It's not a "trick" as much as just common sense.
Buying good quality microfibers is also key, and you can search this forum for such sources. The Pak-Shak is one source. The Rag Company another.
TowelPros.com is another. Any of the car-care chemical suppliers/wholesalers listed within this site sell quality microfibers.
Still not sure what to buy? Try buying one of the sample or starter microfiber kits from them that give a variety of microfibers for you to try out and evaluate for you own use. Yes, you may be spending $40 or $50 to do this, but as mentioned above, its what separates the pro's from the wannabes or almost-as-good.