Decided it was time to clean it the sump today. Made a large batch of saltwater, got the necessary towels, vinegar, pump, and scrubbing tools. Left the wavemakers on inside the tank to keep things moving. Then pulled the power on the pump, skimmer, dosers and ATO.
First cleaned the skimmer, then the pump. Then disassembled the manifold to clean it out. Then used a small maxi jet pump the force out the water into some 5g buckets. Stopped after the first 3g to move over the cheato and marine pure balls. Then pumped out the rest of the water I could. Then slowly took my time to slide the sump out of the stand where it's been for the past 2 years. Into the backyard, where I took a scrapper and hose to get rid of all the nasties that have been building up over that time. Amazing how much Coraline and algae builds up over time.
Then spent time putting everything back together and filling up the sump with fresh saltwater.... essentially performing a water change at the same time. Whole process took about 2 1/2 hours.