All of HOS' FRCs have their uses. Learn them all. Don't worry about lvl2 and lvl3 BRP FRCs though, unless you plan on blowing charge for a faster FRC.
Corner throw I always forgo the damage and do 6HS for knockdown. This gives you a perfect setup for fuzzy guard (meaty j.S land 2K/dj.HS delay dj.D). Go for the kill if it's within reach though.
Learn dustloop. The combo has been posted above. You can nail it in the corner off of lots of things, 6P, Gunblaze, Fafnir, fuzzy guard high option, CH j.HS, anti-air CH 5HS...
For Gunblaze midscreen, run-up 5HS sj.SHD is easiest. If you land it and they're close to the corner, dash and do j.HS j.D dj.HS dj.D x 2 for dustloop.
Gunblaze is mainly an oki and AA tool. Don't throw it out in blockstrings unless you have mad respect from your opponents. On oki you can do a late gunblaze while running to get a crossup, mix it up with 6K or 2HS to keep your opponent guessing.
Make up your own blockstrings, really. Just try to keep things short so you stay close.