A couple years ago, when I was 5'7"/180 something lbs., I was packing a 6" 686 IWB all the time. I just used IWB holsters designed for 4" guns with an open bottom. Honestly, there wasn't much of a comfort difference between a 4" and 6" L frame IMO. It's very doable and those long barrelled .357s hit super hard.
I find that 6 in. is too long for a belt holster if I am going to be sitting. I use shoulder holsters most of the time. A 6 in. M19 is a good carry gun. If the weather is warm I put it on over a tee shirt and then a button shirt but I don't button it. Larry