I haven't taught Guinness how to weave through my legs yet- still stuck working on the limp and trying to get hubby to get down on all fours. Lol!
If you followed my instructions on bow... no wonder Jackson doesn't get it. I just re-read what I originally wrote. OMG!- more info please.
Ok, to clarify... round two.

You have to get on the ground with Jackson and begin by having him stand and face you. With treat in hand, say bow, and in one smooth movement, lead that hand to the nose, then towards chest and finally to the ground- back by his elbows and between the paws.
The goal is to get Jackson's head down (ie; chin to chest), have those elbows hit the the ground and keep that butt up.
Timing is important to mark the behavior you want. Watch the elbows- when they hit the ground, treat and say 'good bow', then quickly get him stand before that butt hits the ground.
To solve the problem where the dog is backing away to get the treat, begin by working with their side facing you instead. Use your free hand positioned behind their bum to stop them from backing up.
If the dog is plopping their butts down, start by having their side facing you. Position your free hand underneath, in front of back legs to stop that butt from downing.
... How about some pics of video's of tricks in progress!