When I first started I was using 10 scrims a day and was washing them everyday aswell, god how things change years down the line, I wash scrims now every other week if that thins weather 1 scrim a week and one for sills.
in the winter I use more, to be honest with you, do not worry how many you use you learn as you go, if you use 20 a day for the first week and earn money who cares your earning money and your scrims with be broken in real quick aswell, you should try a microwipe for detailing they suck the water off and dry very quick aswell.
Good luck and stick with it, we all started at the same place.