Although not scientifically sound methodology, I have found that after a while you learn to build the calibration into your process.....
HLT.....about right.
Mash Tun..... a little high
Hydrometer.....a little low
I know, it's not precise but I make adjustments relative to their readings, and the beer comes out great.
I know, if I ever have to replace one of them I have to start over.