Hello, I like to use things for what they're not meant to be used for

If I put the capo on the 5th fret of a guitar, how can I completely silence the bottom two strings so I can use it as a hackneyed ukulele? Wrapping a glasses' wiper over strings doesn't work.

Try a thick piece of felt folded over and stuffed under the strings. Might be best at both ends, at the bridge and just in front of the capo.