I think SA work best if you have time to take them out on date and pay for the dates too. A lot of girl don't want to be friend with benefit with an allowance. I am very straight forward and tell them I really just wanted to fuck.
Not working too good so far, a lot of the girl agree then back out.
But really. Why would girls in their early 20's want to be dating guys in there 30's or 40's in public.