Sometimes the old ways are better.
They say that necessity is the mother of invention,
well then woodworking must be the mother of necessity.
Over the years I have used countless jigs, mills where I needed to add some sort of coupling to the piece to fit it to the machine, all trying to find a faster way to turn my stepped tenons. I have ground open end box wrenches, made slip measurement guides, attached routers to the lathe, jig after jig, all with the same conclusion; that I was doing it the best way to begin with. By taking my time and slowly turning to the desired measurements. Stopping often and checking with calipers.
I am not a purist in my woodworking, nor am I against using hand tools to complete a job, I am in the middle somewhere and try to do the job the most efficient way I can. For some tasks it means unplugging completely while for some other tasks the power tools can get the job done.
Sometimes the search for a faster way comes to a good end and you find that more efficient technique, but sometimes a slower more methodical route is the best. Only experimentation can tell you sometimes.
No matter what method of work you do, mass producing a piece with machinery or making a one of a kind with hand tools, don't let the tools or technique define your design. You might have to ponder a design concept for years before you figure out how to make it work. Pandering to the tools can steal the creativity from your design and it will fall flat. Draw your creation in your journal(very important for designer to keep) then figure out how to make it happen.
Don't let your imagination get constrained by the tools, but make them work for you to create.
I do still use this aid, but taking my time and creeping up on the measurement, stopping and checking with calipers seems to be the best for me.
If you want to use the slip measurement tool, start by setting up a fence on your drill press and drilling concentrically larger holes in a piece of thin stock and labeling them. Then cut this board in half and when you rough in your turning you can slip it over the work and see how you are progressing.
For the wrench tool, pick an open end box wrench and check it with calipers to get the perfect width. Using a grinder with cut off wheel to take a bit off the end of the wrench then put an angle on it with a bench grinder and sharpen it like you would any other turning tool.
Bring the wrench up from underneath the stock and slowly bring the cutting surface into the stock until it encompasses the work. I don't use this too often, but they are nice to have around.
For tenons I like to add a strip of measurement tape to the top of my tail stock and set my compass to that, then mark the work using the compass.
You might have a better way, that's fine. I just offer tips on what I have found works best for me. The point is to find the best way to make it all work for you to craft your creation.