How much pressure should I be using to pull the rifle in to my shoulder?
For bipod prone, go to youtube and search for videos on "loading the bipod". There are one or two by SH's Lowlight, there is also one by 8541 Tactical, and there are others. Rather than trying to repeat what is said in the instructional videos, watch them and hear it from actual experts instead of me trying to learn and repeat.
I've been going through those and believe I've seen both videos you're talking about. The problem is that they really don't talk about the pressure needed to pull it in.
I believe the videos say to use no muscle pressure and only the weight of your body, through your shoulder, pushing the bipod forward to load it. I was reluctant to say anything because I am NOT an expert on technique and only know what I've learned from video and book sources and personal practice. So I may have it wrong. I use enough body-weight pressure to put some tension on the bipod, but not so much that it skids across the ground.
How much pressure should I be using to pull the rifle in to my shoulder?
not much about 10 pounds of pressure on average ballpark. If you have a 10 pound rifle just lie down on your back and let the butt rest in on your shoulder while the muzzle points to the ceiling. That should be what about 10 pounds "feels" like.
EDIT: Depends on the rifle. I'm referring to .30 rifles. You really need to stay tucked in. This is why people are going to smaller fat stubby cartridges to kill paper. They want to get fat, weak, and lazy and still make a good score. Instead of doing some pushups to deal with recoil they would rather take the easier softer way out and get their jelly donuts everyday. With those barely over .22 caliber rifles you don't have to worry about staying tucked in unless you're an emaciated bantam hen.