are your MCNs SIOs, pockets or AIOs? If you can avoid putting the actual cover in the dryer that would be good. Dryers are really bad for PUL and elastics. If you have to put the covers in the dryer, do it on the lowest setting you can - on the very rare occasions I've put one of mine in I use the "airing" function. Otherwise, I just throw the boosters and inserts in for drying, and lay the covers out somewhere warm