Here is a link to a YouTube video of a young dog running a Zig-Zag lining drill. At the time we
were working on two-sided expectations, being more precise with bumper handling and
developing a better "look". This was early transition work.

The heeling stick was used a few times during the drill for faster sits and Gunny is wearing
his e-collar. Gunny is a soft dog which means pressure must be dealt out carefully. As long
as his tail is wagging, we are on the right page.

I had planned ahead of time to work on one specific problem, but did not want to press the
issue early on in the drill. It is important for him to start sessions in a "fun" frame of mind.
As you will notice his bumper handling became a bit "sloppy" but improved immediately
after "the correction" was given at about 2:08. (note: Watch his tail.)

Cool. Is right/left heeling a preference or necessary for this drill?

Excellent points. I ran into #2 this year after hunting out the boat more than I have in the past. Everything else makes good sense too, I'd like to run a few tests this year with the new pup and may work on this, if I can get used to it anyway