if u have an SLR with a custom function to rewind the film (e.g. canon EOS 33/30/50 or better) with the film leader left sticking out, then it becomes simple. you just have to reload the film as usual when u want to re-use the half-finished roll of film, keep the body cap on (try not to have a lens attached to it), then go to a light-safe place, e.g. place the camera in a light-proof dark bag for removing film, then advance 10 frames manually, by just depressing the shutter. it would help if u have a remote control then u can have it sticking out of the bag.
but i don't have a light proof bag, so i use the storeroom in my house, which is almost completely dark though not totally, then i place the camera in a thick haversack and zip it up and have the remote control sticking out; then i set the camera to shutter priority, snap at the highest shutter speed, 1/2000s in the case of my camera, and fire away till the exact frame where i stopped.
but if u don't have an SLR with such a custom function, then the rewinding will send the leader right back into the film cassette. this makes things a bit more complicated because you must open the film cassette to extract the film leader. if u have a film picker (you can get one from ruby or CP, but it varies in price from $10 to $20 i think), you can just extract the leader easily i think; never tried it.
but if u do not have one, again you need a lightproof bag or, the makeshift solution i use (as above; works for me); then u open the film canister with a screwdriver or something sharp, prying it open, after which you can pull the roll of film out slowly, and you can try to feel around it for the leader (try not to touch the film surface and keep you fingers on the film sprocket holes), then when you've gotten hold of the film leader, you just have to turn and adjust the film until you can get the leader out of the slot at the edge of the cassette where film comes out. this part is...quite simple once you've opened the cassette; you just have to be careful not to touch the wrong parts of the film. after the film leader is out, just seal the cassette back.
the most important thing is to prevent light leaks.
so yeah, it's definitely possible to reuse film that's been shot halfway, but if u've got half a dozen rolls of half-used films with film leaders sticking out, it'd be hard to figure out how many exposures of each roll you've used.
hope this helps