I also just put my dumeril's boa (6 feet but thick) around my shoulders, but make sure she isn't able to wrap her tail or anywhere around my neck.
And I guess a general rule for handling any more defensive snake is make sure their nose isn't pointed in the direction of my face, like Sauzo saidI just push their neck away, or directly push their head off to the side if they're being stubborn LOL. Sudden movements or moving too quickly is mostly what irritates snakes, but not slowly pushing them away.
I measure by letting them slide off my hands and onto somewhere where I'm pretty sure they'll move in a straight line and measure that way. Snakes can stretch out quite a bit when they're moving forward, so if you only measure them while they're curled up like with yarn, it actually gets you a shorter measurement.