It can be challanging.. Most Flying-J stores have special dedicated RV pumps, Generally there are 3 "islands" perhaps only 2 pumps (The outiside "islands" re remotes for the center island pump.. I will leave it to others to explain if you can not figure it out)
I drive a 38' Class A and I find many J's it is hard to exit those islands. Easy to enter, but the exit is too tight for comfort (To date not too tight to exit, just too tight for COMFORT.
Most "Big Stations" (J's. Loves, Pilot, TA
These stations have very large AUTOMOTIVE islands.. PErhaps a dozen pumps or more
Pump #1, and Pump #N (Where N is the number of pumps) are on the OUTSIDE of the area. You can easily pull up to them and get out of there (in every case so far I've seen)
Smaller stations.. here you have to be selective.. Some are simple. Some not so. Example.. On Telegraph RD in Redford TWP, MI, is a Shell. there is not enough room to get to/from the pumps due to curb placement (They have made improvements from what I under stand) but at Grand River and 7 Mile in Detroit is another Shell.. I can (if the pump is free pull off Grand River into the station to the pump farthest from the station 1/2 turn off G.R. Gas up, then exit straight ahead onto 7 mile again making a partial turn to go east, Then I can return to Telegraph and go where I need to go.
(yes I'm from Detroit and useing these statiosn as an example.. GOOGLE maps will show you the stations if you wish The Station in Redford is on the west side of Telegraph SOUTH of the freeway. (I-96) not sure howe far.
The Marathon at Telegraph and 7.. Can be a witch with the Class A.
But Most Wal Mart (MURPHY USA) are not tribble at all.
Look for a station where you basically need not turn till you are FULLY clear of the pumps.