You don't have to attach the metal guide to use the walking foot. Do you know how to attach the walking foot though? It is a tricky foot to install properly. The "fork" on it needs to go around the screw that holds the needle in position; this is the mechanism by which, when the needle goes up and down, the foot "walks" the fabric through.
I'm not sure you could use the walking foot to make twigs and leaves because you cannot sew in reverse with a walking foot. (Maybe just 2 or 3 stitches to lock a seam, but that's it.) It only "walks" forward. It is often possible to work out a design so that you are always going forward, but it takes some mental gymnastics to do it. I'd have to doodle quite a bit to come up with something that would work for that. Nice idea, though. Might have to get my doodle book out......