This is a fairly dumb batch file that, when placed in a folder, will run Google's cwebp.exe (https://developers.google.com/speed/webp/docs/precompiled) against all .jpg files in the same folder as the script. Could be a lot smarter, but it did the trick, figured it could be a good starting point for someone else.

cwebp-all-files-in-folder.bat

@echo off

set /a counter=0

for %%f in (*.jpg) do (
	C:\libwebp\bin\cwebp.exe -q 80 %%f -o %%~nf.webp
	set /A counter=counter+1
)

echo ************************************
echo %counter% files have been processed.
echo ************************************