I drain from the sump. Turn off the return pump, drop in a MaxiJet 1200 with a 1/2" ID hose secured by a stainless steel metal hose clamp. Suck out the crud in the bottom especially from the return area. Change socks.
To fill I drop the maxijet w/ attached hose in the 5 gallon bucket and fill the sump with as many buckets that I took out. Turn return pump on.
I do a 10% wc weekly and change socks every 1-2 days.