Hi there Quantum40 and welcome.
I dont think there is any one method that is 100% correct, but FWIW mine (with a variable temp Makita hg - just with a numbered dial, not digital temp display) is to adjust the temp at least twice through the roast (say, for an average 600 gm batch):
1. Start off at a fairly low temp / gentle ramp for the first 4 mins (approx) - my hg is set at abt 45-50%
2. Increase temp (I increase mine to abt 70%) up to 1st crack (ideally at 10-12 mins)
3. Reduce temp then (mine goes back to 45-50%) for a slow (apx 6 min - abt 3 deg per minute) ramp up to 2nd crack.
I dont adjust the air flow or position of the hg. Obviously, tweaks and adjustments in temp are made through the roast to account for variations in batch size, ambient temp, different bean types, etc. Correttos are fairly "hands-on" roasters (which is one of the appeals for me). I rely on my temp probe/dmm to monitor how the roast is progressing (as well as sight, sound and smell).
Hope this helps. Whilst a bit difficult at first, after a few batches it will become second nature. Cheers,