First, I find it a little odd that the buspirone might be affecting you sexually. It's often used to help alleviate sexual problems like anorgasmia or delayed orgasm caused by SSRI's. So to hear that it might be causing the problem is interesting.

Something about buspirone though; are you taking it in a consistent pattern? It's a flaky drug so you have to take it exactly the same way every time. With or without food and the same time every day. So if you take it with food, you always have to take it with food and on your schedule. Personally I take it at 9 AM with food and at 9 PM without food, every day, always the same.

So overall, I would take a look at the buspirone and how you're taking it.

Second, and in answer to your questions ... both actually. Getting more worked up with more foreplay should help speed things up when you get to the deed itself and regardless of any issues, lube is always a good idea.