It definitely lingers.
For what I've read in the past about it on the internet, the beauty of figging is that the recipient doesn't know what they've gotten into before it's too late, because the pain builds up very slowly, and for a few minutes the newbie "figgee" thinks this isn't as bad as they expected, then it kicks in, and before they know it they're squirming in delicious agony, and then it takes time for this to go away after removal.
So it's like, you get the effects of what you've done a few moments later, which is perfect for some people who want to push their limits or their partner's this way, by removing the ginger root when it becomes too much but it still gets worse for a minute or two.
I can find you a link or two for tips, safety etc. but most of the links I bookmark are about how to top (i.e. do it to someone else), but I assume they'd still be useful.