njrick:
You can ask the soon-to-be recipient to cut her (his?) own switch. The standard I've heard used is to cut a switch of a thickness that the base is as big in diameter as the intended recipient's little finger (so for a smaller child - if it's a child - the switch would be thinner).
Purportedly, apple and peach trees can also supply very whippy switches, although I've heard that willow is the most effective--I don't know if the 'weeping willow' has a name relevant to being the receipient of a good switching, but a supple willow branch does very often have that effect on the person receiving strokes from it.
Assuming that the switching recipient is sent to cut his/her own switches, the disciplinarian should make it clear that any inadequate switch will be replaced by two more-than-adequate ones. So if you're sent out to cut (and possibly prepare) two switches, but one of them isn't deemed suitable (too thin, short and/or inflexible), then either you or your punisher will replace that one with two more effective ones--meaning that three switches rather than two are going to be worn out on your bare bottom before your chastisement is completed.
Depending on the amount of privacy available and/or the degree of semipublic embarrassment desired, the victim may even be forced to cut his/her switches while evincing partial or total 'southern exposure'... --C.K.