It's worked well for me for over four decades. My attitude is if they fukk it up then tough, I don't want to know. Saying that though she is pretty good at the decorating and painting stuff. and it gets me out of doing it.Nooooooo, That's a failed experiment right there, sounds good on the surface but the end result is not worth the risk.
You just need to train them right from the beginning.
See now this is were you went wrong. Any clean up should have been done by them under your supervision and the finished result subject to your approval.The clean up took weeks of tongue holding. In fact I am so traumatized by the experience that while writing this reply I vomited last nights curry & chips into my coffee and drank it without noticing the difference.
The lesson is don't let em do it by themselves, just don't.
Failing that, again let them crack on, your herself would have got tired of her fukk up pretty fast when it finally dawned on her that her handiwork looks cack. That's when the supervision and approval by you comes into play.
By sorting it yourself they have learned nothing and will continue their fukkwittery, they must be shown there are consequences for said fukkwittery.