I stutter on all the things, it it varies on context and tbh I don't really know the triggers. H and I, I stutter on both and both just sound like I'm breathing really hard. M, a long hum, but most of all I stutter on hard or popping sounds. That's your hard B, T, P, etc. Generally it's little more than 3 or 4 repealtitions before im able to get it and move on. I don't have any tricks, I just generally know what I'm about to stutter on and find a synonym. Works like, half the time. Otherwise, for those popping sounds, trying to smooth out the sound. Instead oh the hard "buh" with B, you'd say it softer and a little more drawn out. I am perfectly fine with people finishing words for me, let's me move on quicker and avoids extra embarrassment. About characters, I don't know about everyone but for me, my stutter is just about the only thing that offends me if someone mentions it with any shimmer of negativity. If they're just curious, okay. If they fake repeat one of my stutters I absolutely cannot stand it. The worst offense. As far as showing it in writing, I've found it difficult. If it's a light stutter I think adding the "t-to" extra character hyphen works fine. If it's a bad one then maybe some extra letters, then outside the quotes describe the stutter some. Something like: "..." he said, stammering horribly. Not very nice but it would get the point across. If it's on a soft sound like and H you might do something like, "huuuhhorrible" Maybe a little awkward to read, most people don't stutter in books, and those that do most writers say the character has a stutter in their introduction and leave it at that. That's my bit. Hope it gives you some ideas.