Got it by trial and error! Yay!
For everyone's reference (everyone in the world, because no - google
does not know how to do a hard reset on a Uniden Solara until this very moment...)
Hold down DSC and Up while turning on. "DSC" will flash on an otherwise blank screen
With the unit on, hold down select and Hi/Lo for about a minute (unit will chirp).
Turn off, then on again - unit is reset!
I'm going to go back to all those forums
where people asked the same question and answer them all.