I suppose it’s how limber you are…
TIP: HOW TO FIND RAFTERS: MAGNETS!!! Any neodymium magnet, like from a computer hard drive, will strongly stick to a sheathing nail - they will stick even though arch shingles. If you want to have fun, get some neodymium ball magnets and you can get the precise nail location, in fact all of them on the rafter which can help when encountering sheathing end nailing.
One way is to shingle as far as you can and then put in a row of jacks. Problem with this is the next shingle course will be at your toes as you cover the jack ends. I have to sit on the plank to do the next couple courses. Alternating between standing an sitting is a Royal PITA.
Other way is to put jacks down and then shingle over them at least 2 rows before working on them. Issue with this is that your jack rows are now closer by the number of courses above you shingled.
I’m doing 7 in 12 pitch which is 30*. The plank is 2x10 and the jack is 45*. To get a level plank, I lay a 2x4 underneath at the roof end or the jack.