Let me systematically go through your questions. I think you will begin to see why I am hesitant in always giving a single simple answer. When dealing with worms, the most common answer is “It depends”.
Dampened Newpaper, coir, or leaves?
No problems here (Depending on the type of leaves). My bedding of choice is newspaper that has been soaked for 24 hours. Both coir and leaves will also work, but both have some drawbacks that make me prefer newspaper.
Decaying Food scraps,oatmeal,etc.?
Produce scraps are okay, although there are certain items most want to stay away from such as citrus peel. Frankly, I have yet tried citrus peel in The Worm Inn. Because of the air flow, it may just handle everything. Not sure yet.
Avoid mixing grains such as oatmeal throughout your bedding? Grains can sour your bedding, making your worms want to lay on top and rot. Grains are best used as a top feed and not mixed in.
Soil, peat moss, saw dust, ground up leaves, etc.?
Soil does nothing for composting worms but add weight to the bin. I’d avoid it. I’ve never added any soil to my worm beds, and have never had any issues. You’ve got all the bacteria you could ever need in you worm bedding that came with your worms.
Peat Moss is an okay bedding as long as it has been rinsed a few times. Canadian Peat Moss is very acidic, and can cause problems if it is not soaked well, and soaking it multiple times is a good option.
Saw Dust can be horrible depending on the type. For example, Redwood sawdust and worms are a bad combination. In my experience, the worms will not go into it. I have not tried many other types of sawdust because newspaper or cardboard work so well. I’ve heard some of the hardwood sawdust works well, but until I try something, I’m not going to comment on it’s success.
I’m not a huge fan of leaves….they don’t hold water well, and they tend to get messy as they break down. Paper/cardboard is clean.
The bedding material on top is used to create a barrier so the bugs do not smell the rottig vegetation. Want to test this theory?….leave some sweet fruit on top of your bedding and see what happens! I call this, “Fruit fly fog”!
Even though The Worm Inn already has the nice screened top, bugs will find a way if you do not maintain a thick layer of bedding.
The castings in The Worm Inn will fall to the bottom of the unit. You will end up building up a good amount, pushing the damp food and the worms to the top. When you have enough castings built up, simply unlock the toggles on the bottom and milk The Worm Inn like a cow. When you hit some unfinished stuff, simply close the bottom, lock the toggles, and throw the unfinished stuff back in to be reworked. Because the castings have had a chance to dry, most of your worms are going to be in the upper layers with the damp food. For more instructions on The Worm Inn, go to http://WWW.TheWormInn.Com.