Howdy, I go with the burp thing. You'll know it when you see it.
Yes indicators are garbage.
One thing that is over looked is to make sure your black tank is well above half before dumping. I know hooking up and then dumping after 2 days is fun and exciting but WAIT. With just the 2 of us it takes a full week to be near full and that's using it a lot.
We stay in an RV park for months some times and generally (except Texas) leave the grey water open. A day or two before dumping the black I shut it off for a day so that we will have adaqute water to flush out the sewer after a black dump.
One other thing I buy some Pine sol for a buck at the Dollar store and dump about a third of it in the hose after a black dump, shake it a bit to make sure it is in the entire hose, wait a few then dump the grey. It isn't fresh as a daisy but better then if I didn't.
Happy trails.
K.I.S,S is always the rule of the day. Been doing this stuff for 45 years. am 67 now and has worked why fix it.