The pump to empty the grey water tank is also one. When using a portable macerator pump, I'd have to make sure I have both pump buttons nearby, so after emptying the black, I can cycle the grey tank's pump to fill up somewhat, then cycle the external pump to get that water down the hose. I might end up letting the grey tank fill up into the black and then flipping the portable macerator pump to eject the contents, but I'd have to do that twice, since the black tank is 11 gallons, the grey is 14. I do know this backflushing will do a good job at ensuring the black tank is clean of all but the most tenacious stuff though, so it might not be all bad.
