Hi, I've used that library before, here's a few demos:
Mine:
https://www.youtube.com/watch?v=ue0e-GpTGbg
The creator of the soundfont:
https://www.youtube.com/watch?v=QEX-wPn4cHk
There's an xml file that contains the GUI for the instrument, load that instead of the sfz file and you'll get a custom interface for the soundfont in sforzando, it makes it a bit more intuitive. The instrument is basically a bunch of key switches that activate different sounds like mutes, harmonics, slides, etc. Each key switch changes the sound of the instrument, so in your midi track you'll have to activate the key switch you want just before playing the actual notes, you can see the key switches in a grey-ish color in the sforzando piano roll.
As for using the soundfont for blues and other generes besides metal, you should have no problems with that, the soundfonts has clean (no fx or amps) guitar samples. All clean guitars sound the same, so if you set up you amps and fx for a blues (crunchy instead of distorted) it will sound like a blues guitar. You can look for tutorials on youtube on how to get a blues sound, even if they use a real amp, those techniques should apply to virtual amps.
Cheers :)