Depends if you just want it done or done neatly.
The problem often comes when the person not doing it wants it neat but expects it to be done in sloppy job time.
Often the person not doing it fails to account for prep time. Stripping, clean up, wash down, inspect for problems, fill, wait to dry, sand, clean again, fill the holes you missed/didn't spot, wait to dry, sand, clean again, sand the woodwork, clean again, clean the stuff you already cleaned more than once, check, sand bits you missed again, clean it all again, size, take hsndles and fixtures off or protect them, ttmasking tape stuff you don't want paint speckles all over, cover the flooring and/or take it up, check your supplies, find you forgot the brushes/wrong size brushes, go to the shop, put down dust sheets or you'll be finding specks on stuff for years, clean again or you'll be picking bits out of your paint with every stroke, apply size and wait to dry, measure the walls, work out your wallpaper's repeat, cut paper, realise you measured it wrong, cut more paper/go to the shops to buy more paper. There's a few more bits but I am bored now.
After all that, your sick of FUCKING DECORATING now, wish you had never started, it looks like you have done fuck all. Then your other half comes in, starts making comments about how long it's taken so far and when you gonna be bloody finished you lazy git.
Then you have to resist the urge to tell your other half to fuck off and do it themselves if they think it's such a quick and easy job.