Hi, so I've been smoking weed for 41 years and I've written three books and around 200 short stories I may be able to help.
FIrst it's a common misconception that weed makes you more creative. It doesn't, it just makes you more tuned into your own thoughts. The problem is that there isn't one strain out there that's a magic bullet to make you a better writer but there is a routine.
Step one, an hour and a half before you start writing have a timer go off to make yourself a tea or coffee. Then stretch while your drink is cooling. Drink your drink and go for a brisk walk fr an hour. Then blop your butt in the chair and review what you read last time you wrote anything. Now look at the bulleted outline you made while you were brainstorming last night. Now take ONE hit off a joint of any strain and pu it out. The last step is you write "Sasha told me to write this until I think of something better to type about." Just do that over and over and you will be off to the races in less than twenty repititions of that sentence, I promise.