With practice you just learn how to do it. Just don't get so empty that you can't pass up a station that is a little too tight. The worst problem that I have ever had was having to wait on someone that got gas and then decided to shop in the mini mart while parking me in (has happened a few times).
Think about the fact that the gas is delivered on an 18 wheeler and they pull in there.
As far as diesel being more difficult, I suppose it can be at some stations but if I had a diesel I think I would be using the truck stop big truck lanes as much as possible when towing.
I did see a gentleman take a very new looking truck and 5th wheel combo and manage to not think about the trailer taking a inside path to the trucks path and literally ripping the axles off of it on the bollards that protect the gas pumps. This was about 1/2 mile away from a camping world on an exit that has not much else on it. I hope he didn't just get the trailer minutes before.