I've just acquired an end-feed shuttle and have been trying it out with 8/2 cotton and 60/2 silk. Do you adjust the tension for different weights of thread? What's the best way to hold the shuttle—with the exiting thread toward you on the right side? Is it okay that your thumb is on the exiting thread as you throw the shuttle through the shed from the right? If you throw a couple of picks in error and need to unweave them, how do you deal with the threads—with a boat shuttle you just wind them onto the bobbin with the flick of a finger? Any tips would be appreciated!
When you throw a boat shuttle, the drag of the rotating bobbin pulls the weft snugly against the selvedge thread (after you've determined exactly how to throw the shuttle for optimum drag). Instead of a rotating bobbin, the end-feed shuttle is equipped with a stationary pirn. The yarn is pulled off the end of the pirn as if off a cone and passes through a tensioning device. The tensioning device can be a spring that you adjust or a series of hooks you pass the thread around. You do have to adjust for different yarns (very thick yarns will have a different adjustment from very fine yarns). When you are ready to weave and have wound your pirn, throw the shuttle and then tighten or loosen the tension as needed to provide the amount of drag that works for your warp width and yarn.
When you weave, you keep the shuttle always in the same orientation, with the exiting thread toward you. You don't turn the shuttle, which means that in one direction the exiting thread is at the leading end of the shuttle, in the other direction, at the tail end, resulting in more drag on one selvedge than on the other. You therefore have to adjust the tension so that the drag on one selvedge is an eeeeeensy bit loose and on the other selvedge an eeeeeensy bit tight. (But you wouldn't want to take the time to turn the shuttle as you weave to equalize this effect.) You shouldn't need to use your thumb as an additional tensioner (but if you have it on the shuttle as you throw it, it won't stay there as the pirn unwinds, so no worries about that).
Try not to have to unweave! (You can't rewind the pirn.) If you have to take out more than a couple of picks, I'd cut the weft out instead of unweaving.