The 24 has a signal strength meter as do ALL Directv boxes.
Setup menu, satellite, signal meters.
You are correct, there is no "lock"per se. You peak the signal then your done.
Several turns won't make much difference, I point one leg of the tripod at the compass heading and and loosen the leg set screw to move change the angle to peak. I use wife on iPhone method to peak signal.
You really dont need to change the skew and tilt once set for your area unless you are moving hundreds of miles. Moving north and south changes tilt which I tweak with the sat box anyway.
I set up my SL3 HD SWM probably 20 times a year, maybe more.
Set everything to the defaults, have mast plumb, the point the LNB close to the compass heading, then move back and forth to peak signal as your signal reader watches the tv.
I never use a meter by the dish.
If you want one there are used Bird Dogs on Ebay right now $260
that powers the SWM, you dont even need the sat box connected.
ClickyAlso, one more tip. If you turn on the sat box with out the LNB and power inserter on it often goes through its diags and then wont recognize the LNB after you connect it and you have to power down the sat box to reset it. Sometimes hitting the red reset button will fix it but unplugging it is a sure thing.