Sorry. I misread your original post. Since XSLT can be rather complex, my recommendation would be to do it by hand.

Don't rely on a script that performs XSLT -> TT as they are radically different. Creating a generic script that would take an arbitrary XSLT style sheet and produce a TT template file that produces the same arbitrary output, would be very involved. Creating a script for specific XSLT style sheets that produce very similar output may be worth it if you have dozens or hundreds of style sheets to convert to TT.