I think it also depends on how many enemas. If you take a few enemas in a row, then the last ones should have much less faces left, mostly just water, and so a little leakage is not too bad.
I prefer to have a few enemas, but have the last two shorter with less water, so they are mostly just a rinse of the rectum and early colon, not likely to simulate too much deeper. Then anal play is usually clean.
But if you really want to be sure, then wait an hour, or even two.