The straight blast is definitely one of my favorite all time techniques! I like to go into the blast right after nailing an opponent with a good stiff straight punch on entry or out of a trapping situation! Just remember, if you can land the first punch, usually a blast will fit in nicely if you follow up immediately with no hesitation whatsoever! Especially if you can stun the opponent or crush their snotbox with the first shot!
The whole idea behind the straight blast is that the brain is bouncing back and forth against the inner walls of the skull like a speed bag as you are pounding them with the blast! This starts a series of minor brain concussions that can result in unconsciousness rather quickly if your punches are landing correctly! Bruce Lee wrote about this at one point and it was later published in a Hong Kong Jeet Kune Do publication! I am fortunate enough to have it!
Sometimes if you can catch the opponent in the knee with a straight kick on entry you can go right into the straight blast from there! The body alignment from the straight kick works well with the blast. Once you start blasting, don't let up until the opponent starts to fall!
As far as follow ups, if they are still standing (for some strange reason), I agree with Frank! Headbutts, knees and elbows fit in nicely here! If they fall (should happen), try to catch them with a straight kick as they go down! Be neighborly and help them fall faster! Depending on the seriousness of the situation (and whether or not they are still conscious) you may want to kick them or stomp on them a few times after they are down! Of course, if they've had enough and the conflict is resolved, just let it go!
The chasing step, which is a rapid series of push shuffles, is the preferred method of footwork to use with the straight blast. This works really well from the Seattle bai jong foot alignment, as the groin is protected by the lead knee in case the opponent's lead leg comes up as they fall backwards! It would be quite embarassing to catch one in the nads from a falling opponent, especially after you've just totally re-arranged their face! I certainly don't agree with the "just run at them" approach to the straight blast! You can't really control your momentum using this approach! It would also be embarassing to just clumsily fall all over your opponent as they go down because you couldn't stop yourself! I mean, what would you do in that situation? Just hop to your feet quickly and say, "Of course I meant to do that!"
For drilling the straight blast, I like to have my partner hold a focus glove at head height, using one hand to backup the glove for firmness of position. I start to punch and he moves back at a realistic speed as I pursue, blasting the glove continuously. When he drops the glove I continue punching for a few more punches. This trains you to regain a target if you lose it. Also have your partner suddenly drop the glove to groin height and practice kicking immediately to the glove with a straight kick. This trains you to kick immediately if your opponent starts to fall! I also like to stand in a neutral stance in front of a wing chun wall bag mounted at head height and blast away at the bag. This develops short range power, penetration, correct wrist alignment and speed into the punches. It also conditions the knuckles for impact. A bag filled with sand or BB's is my favorite, although most practitioners have to gradually build up to this!
I also like to work the straight blast on the mook jong, using the dummy arms to bridge off of. Punching between the arms also develops your economy of structure and your accuracy! Be careful not to impact with the trunk of the dummy improperly, as this can really damage your knuckles! Good luck with your straight blast training and I hope this is helpful to you!
Sifu Lamar M. Davis II
Jun Fan/Jeet Kune Do