I've cut a bigger round hole in mine, so I can pressure wash it better; and of course the transfer pump will fit through this hole. I bought one that held PVA glue, which probably wasn't the brightest thing I've ever done.
I've been pressure washing it for about an hour, with a baby domestic pressure washer, and for the little bits of floaty PVA glue that I can't get out, I'm going to 'black-nasty' (gaffer tape) a ladle to the end of a short length of modular fishing pole, and scoop 'em out.
I'm taking a break from it right now.
Sigh!