If he has problem with getting caught in guillotined on a double he doesn't want a head outside. Ankle picks work great for me personally.
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Outside single doesn't get your head inside like a double though. When you finish a double you use your head against the body to finish, on a outside single you slide on the outside to pick the leg and from there you have options. Like I mentioned my preference is to circle it down, some pull it straight up or like I also mentioned you can go with a trip. Outside single is very similar to a pick.