Honestly what i need are other punishments that will work. I have tried making them scrub the walls and base boards but they think it's fun

I have tried grounding,spanking,yelling,talking,time out everything. I have even now resorted to going to the bathroom and standing in the door way when they use the bathroom because they can't be trusted. An 8 yr old and a 3 yr old know right from wrong they can follow rules so they should be able to play in their own bed room without me sitting right there. Not saying i would leave but if i get a phone call or need to use the bathroom or if i want to watch a tv show they should be able to follow rules and play without all this crap. This is what i don't get?