I think random really helps too. I stop and if my horse's nose moves in front of me I back her up and out of my space. If she keeps walking once I stop I tell her to pretty much get out of my space now and keep away from me.
Why are you walking her back and forth across a pasture? It's often good to get out of the pasture because that's their "home" or "rest" place, outside is work. I'd spend most of my time getting her moving from pressure rather than leading her around. Teach her to back up out of your space, yield her hind and fore. Then I'd start leading and when she goes to move into your space I'd push her right out of it with you'd taught her, once she was back to where she should be I'd continue on.
Slapping neck etc doesn't do much. An elbow out might work with a horse getting out of line but if your horse hasn't been taught then it's not going to help a lot. Horses work on pressure and release. If you're training the horse to back up and she puts her head in the air, if you release the pressure you're training her to do that. Teach her to lower her head, back her up with chest pressure and always stop immediately when you get what you want.
From what you're saying I'd be doing a lot of the real basics, like tossing a whip/rope over her in a passive way so she's not scared of it, touching her all over and again moving from pressure. Stuff like lunging comes later when she's comfortable will all the tools and understands forward/back etc.
Right now I am walking her back and forth across the pasture because I do not have any designated places for work --- this will eventually be corrected -- hopefully with a round pen
She is definitely not scared of whips or lead ropes and has been handled extensively --- except for getting her to give me her feet
I definitely want the real basics with her --- I believe she was advanced to new tasks before mastering the primary tasks (someone got in a rush with her) --- it's not a mistake I want to repeat
Leading seemed to me to be the first basic lesson so that is what I am trying to start with
The only reason I was lunging her was because she took off running when I tapped her with the hog stick (no whacking or hitting -- just a tap-tap) -- so I figured lunging would get it out of her for a little bit and go back to what I wanted to work with her on
After the lunging she was a little more compliant and was able to follow with very few issues despite changing directions often