Sometimes I'll transition to full guard from 3/4 Guard or Pyramid by working in an underhook on the arm that's controlling my leg. Dig your arm in (usually best to find space between your leg and their body) and pull the underhook up towards your head, stretching them out. Hip escape out to the side of the leg that's trapped and free the leg to full guard.
Usually from here I'll start to work for Prison Guard by keeping my underhook, letting go of the overhook and joining my hands together. At the same time I'm continuing the motion of my hip escape, trying to get an angle to establish Homie Control. From here I'll start trying to bring the arm over to Prison Guard.
A lot of the time if you get a good underhook on the arm, stretch them out well and make your hip escape continuous all the way to the other side, you'll find that the arm is nearly half way over to Prison Guard by the time you get your hips out. This is usually good, but you need to be ready to lock it in tight if they swing their arm over quickly, trying to suck their elbow out the back.
Its pretty much just a basic way to re-guard to full guard from 3/4 Guard, but because I get the underhook and my hips are switching all the way to the other side I'm half way to Homie Control (and because you didn't want Meathook / Kung Fu options).
Also, if you keep the over hook after you have pummeled in for the underhook on the far side and switched your hips underneath them; instead of freeing the foot to go to full guard you can start to use your hook to elevate them to the overhook side, using the other leg to block the outside of their leg.