Using dildos, check. Got myself a 10-incher and practiced in the shower. Found it was pretty easy--don't try to breath. That was how I got over the reflex, the first time. Just held my breath while sliding it into my throat. After that, just more practice until you can be roughly face-fucked without gagging. I'm getting there but it's hard to find someone to practice on.
Don't suck cock for the guy. Suck cock for you. If you really want to suck his cock it will be easier to get past that reflex. 11 inches is no problem now.I used dildoes to train myself. If you get the urge so suck and can't fit anyone into your schedule, a nice long dildo does the trick nicely. Also a nice hit of rush or jungle juice lets that fat dick slide in real nice.
One thing to remember is to breathe through your nose even if your nose gets stuffy; in this, your body will automatically make you breathe through your mouth and with a dick in it, could trigger your gag reflex. Cock suckers seek to eliminate the reflex... but I don’t think that’s a good idea since the reflex keeps you from choking so tame it instead of trying to make it go away.
I've never had problems with gagging, but then I don't usually take guys that deep. That said, I used to play with a guy that liked to thrust vigorously when he was about to cum. Once in a while , I'd find his cockhead positioned uncomfortably at the very back of my throat. I also found that swallowing hard a couple of times would make the gag reflex subside. Position also seems to make a difference. If I'm on my knees, kneeling in front of him, I can take him all the way back with no difficulty. Perhaps I feel more 'in control' that way.
