Building trust?

[redshepherd]

but just get him out like normal, hold him for 15-20 minutes (long enough for him to calm down and get used to the fact that he’s being held), then do it again the next day. The only way to get them used to being handled is to handle them. And more importantly, the more you interact with Hector the more you will build your own confidence and trust in him.

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This isn't accurate. Over-handling these snakes also causes stress and can make them more defensive, and continued over-handling can potentially make them ill. Short, calm handling sessions for 5-10 minutes every other day even would be fine. End each handling session on a good note.

As for his hissiness, it could be that he's in shed, or it could be your husbandry is off and he isn't feeling secure or comfortable in his cage. You've only had him a month, so he could be gradually becoming stressed due to incorrect husbandry. You can post your setup here if you want.
It could also just be his personality in shed, some snakes get a bit hissy when in blue.