When I do a search of my complete C:\ drive
Particular reason for that?
I'd think it to be rather inefficient.
Might the issue not be the fonts, per se, but perhaps the number, extent of files that you are searching through?
For "finding", there is nothing better then
Everything.
You can search for ext:fon to find all "font" files.
You can search for ext:fon !C:\Windows\Fonts\ to find all "font" files not found in C:\Windows\Fonts\.
But then, are you even looking to do anything (in regards to BRU) with "fonts"?
If not, then just what are you looking for (in BRU, i.e., why are you searching all of C:)?
Find said files in Everything, & drag those you're actually looking to rename into BRU.