Biggest, wait till they are gone, school, play groups, daycare, overnights whatever and have it. Yeah I know the last thing you want to do on your only bit of free time to rest is declutter, but get it done then or just add to the hoard.
Two, since my youngest is hardly ever not with me, she stays with my parents when I work and once in a blue moon she'll spend the night with them. I run up to my place on my lunch break and drag out bags and put them in my trunk till I have a chance to run by the thrift store and drop them off.
Three, okay you don't work and your kids are never out your sight...wait till they are alseep then take the bags/boxes to your car. If you don''t have a car, then take them wherever and yes I will probably get some heat for this, even your dump, if the stuff is in really good condition and you are allowed to leave them open sitting outside and someone might come along that can use it.
Step two and three take some prep work, you'll need to be able to quickly get them gathered and gone..I have 2 baskets in the living for toys..One basket is for good toys the other I put toys that are not played with alot, stuffed animals (b/c they have a zillion of them) things of that nature. They don't know it but the second basket is a cycling donation bin, when its full I donate. Honestly they never notice, and it saves me the headache of fighting with them.
Okay for those that I'm not teaching my kids anything...okay I see your point, but they know I donate, they see me donate clothes they have outgrown, dishes I no longer use, change to the bell ringers during christmas. My teenager, isn't as bad as she used to be, but she is still a pack rat. My four year old you would think I was killing her if I tell her I'm going to donate her rattle she hasn't used since she was a year old. I say why put her and me through that when I can avoid it.
This year though I'm trying the one in one out rule since my parents want to buy them something every time we turn around (what else are grandparents for but to spoil the grand kids) but we will see how that works out.