I provided some nappy sacks (2 or 3) pegged to the wetbag for putting pooey nappies into before putting in the wetbag.

And I did a short, to-the-point list of instructions that they stuck to the nappy change wall for anyone who was changing nappies to refer to. Basically: for wet, do this, for pooey do that, don't use any creams I don't provide, don't rinse, soak etc., do up as you would a disposable.

No-one had any issues with understanding, just some comments that it was easier than expected.

HTH