I generally lay with my butt propped up for about 10 to 15 minutes. Is it helping? Is it necessary? I don't know. I like to think it helps though, plus I enjoy that time to sit with DH.
Here's what I know- Generally the stuff that leaks out is the stuff that isn't so great. (Old, dead, confused sperm etc). When a man ejaculates in a woman, the good swimmers get a really good head start of where they need to go to catch the egg but the sheer ejacualtion alone. So, they say that you really shouldn't worry about what leaks out. As long as you have good quality fertile cervical mucus to help the sperm find their way, I wouldn't worry
To be honest, there are times where nothing leaks out and I've asked my DH if he actually "did his thing" LOL I'm so used to stuff leaking out!
I think if you want to prop your butt up or lay down that's fine... Another thing to consider- women have been getting pregnant for years and years using so many different positions and scenarios... so there's always a chance! Good luck to you!