Sadly, I use chronically enough that I sometimes have to ween myself down from high to normal just redosing with gradually smaller amounts until I'm just totally normal for the rest of the day. It's pretty effective, but that assumes a lot of things, like you didn't go through your whole stash already. 8)
Yeah, I'll agree with shreddedlettuce. You only have so much seratonin/dopamine. You can't really do much to speed up how quickly or how much of it you produce. You can only make your body dump all its reserves at once. I may be oversimplifying a bit, but once you're out, you just have to wait before you'll be able to feel the euphoria and rush again. So, it depends on how much you've already done and whether you're a chronic user or not. Don't get burnt out, it sucks. But I'd say you can usually redose a couple of times before you hit a wall and it's basically just powdered coffee. You've gotta be a really heavy user for it to be totally pointless. You'll pretty much always feel more awake and focused, even if you can't get to that original high.
In the future when coming down, a simple option is melatonin. My buddies and I all take it to chill us out and help us get some restful, recuperative sleep so we can do it again the next day! Obviously it's convenient because you can get it at the drug store, although it's somewhat pricey.