When your youngest experiments with redecorating your walls with a Pollack-esque crayon drawing, do not try to remove it with oil and heat, scrubbing intently until there's a gigantic magenta smear on the wall, (instead of the less-intrusive scribble). No. Instead, go out and buy yourself a Magic Eraser, don gloves, and scrub that smear into oblivion. Then reflect on the fact that if you had just gone out and bought the (somewhat toxic) cleaner in the first place, you could have not had the shadow of the smear, along iwth oil residue.
Ah, good (green) intentions last until we have to deal with Crayola.
That is all.