Working instructions for Font Awesome 5.8.2 
tested with Font Awesome Pro 5.8.2 (also works with Free)
### Just in case I forget:

1.- Download *Webfonts* package
2.- Visit http://fontello.com
3.- In Finder, navigate to folder `Webfonts`,
drag & drop `fa-regular-400.svg` into fontello
4.- In name, enter anything, I used `fontawesome-pro-reg-5_8_2.svg`
(just remember to use lowercase and no spaces) 
5.- Drag mouse to select ALL icons in section `Custom icons` (unintuitive, I know), takes some seconds for the browser to become responsive 
6.- Download button becomes enabled 😄 , download! takes a couple seconds to start, wait for download to finish.
7.- Click `Clear custom icons`
8.- Repeat steps 3-6 with `fa-solid-900.svg`
9.- Install TTFs, 
10.- In Sketch install SVGs
11.- Profit!

_Based on a comment by @mamuts12 in https://github.com/keremciu/sketch-iconfont/issues/170#issuecomment-474819026_ 💯 