| Cranky_lizard |
I know this is old but I just answered this somewhere else so I might as well put it here too.
In order to move a creature that you are grappling, you would use the Drag action.
The check would be an athletics vs target fortitude (1 grapple action). Then to move the creature, you drag. I feel like this would be another athletics vs fortitude (1 action) to force the movement, and a drag (1 action) movement.
In this case, you use half their creature bulk + bulk their carrying (depending on who/what). If you have enough strength left after your bulk ( you can carry a total of 5, you're carrying 2, and the creature bulk total is 2 so you could drag this creature). If the bulk is over what you can carry (same example except you were carrying 4 bulk), you could not move the creature at all.
Max movement according to dragging rules of approx 50ft/min, this would give you about approx 10ft to drag the grappled creature.
Pg 272 for drag and bulk rules