Can someone walk me through applying a patch posted on Github?

You just need to install the Github version. Look at the bottom of slic3r.org page for the instructions.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

ooops! Tee Hee . Thanks for the info! The instructions are quite clear.