I’ve had to do this twice on a 6000 series for my stepdad. Just have to drain the tank then remove the shut off and the fitting from the bottom of the tank, if I remember right it just had a copper sealing washer. I flushed the tank then used a air powered suction vac to remove anything left. He fills his with a five gallon can and always spills some which collects dust and chaff from bush hogging, and each time he fills it some gets knocked off into the tank. The first cleaning lasted about two years, the second time I cleaned it all out again, I removed the pre screen from the tank fitting. I did install a cheap metal inline filter from the parts store to act as a pre filter in the hose between the tank shut off and the main filters. That has lasted 5 years now with no issues.
As a quick fix, just blow some air backwards into the tank outlet as said above, and this should by you some time if your in the middle of a project you need to finish.