How do i trigger the sex event with Everett?
Go to Northcrest at night and explore the place. At random you will see Everett and an other guy having sex on the streets.
With that info you can leave and confront him later about it or right after they are done.
With that done you can go to the Outpost and then speak to him the option to have ,,Fun´´ with him should appear if you have picked the right options that is.
Just be teasing with him and dont blackmail him.