waste tanks are not very deep but are wide and long usually sloped from entry to exit. But the drain line comes out the side so there is a lip.
Tilting the rig side to side is not necessary. Tilting front to back can help when dumping.
Completely draining of tanks down to the last drop is not necessary. Fact is you should put some water back into waste tank especially black tank so bottom of tank stays wet.....that way 'stuff' left behind doesn't dry out and stick. Can be very hard and difficult to get that dried stuff out later on. Also with a wet bottom new stuff doesn't stick.
I always flush 2 full toilet bowls after dumping/rinsing of black tank.
Leaving a bit of water in tanks won't hurt.it'll help.
So no need to do that bucket draining routine at home.