I think alot of it was pretty well covered in your thread in shaving help.
The problem with the neck and jowls is the skin is usually extremely delicate and often the beard is going in all sorts of directions so that's where extra attention to prep should really be. If you are face lathering its easy to fall into lathering the cheeks and facial area because it's easier to do, just make sure you cover all areas equally because it will lift and help soften the beard and so help with the overall shave.
Map the beard really carefully.
If you can't shave atg (something I like to avoid btw) look at mantic59's videos on advanced techniques, maybe try an XTG pass from the "other" direction.
You could also try to introduce some gentle skin stretching around the jowls by cranking the neck or contorting the jaw a little, have a look at a few straight shaving vids to see how that's done.
Your skin and beard is still getting used to the new regime, it'll come.