egg shells break down quite well I use it in my compost, I also leave mine uncovered to allow insects in to break it down quicker and allow air and water through it, as for mulching it is basically covering up your soil to allow it to retain water, kind of like natural growth leaves and moss would do. you can use wool, cardboard, grass cuttings, sawdust, egg shells, bark cuttings etc for the more natural way rather than plastic sheeting. if you are in a colder climate using gravel or small rocks to retain heat helps as well.
I use horse manure as well as I get it for free, you can always ask anyone near you if they have a horse, or any stables near by, they often will allow people to come in and take it away as it saves them dealing with it.
I know a lot of people round here who use a bin bag filled with manure and compost and plant tomato plants in it, kind of like slicing a compost bag open when it is lying flat and planting your seedlings in it. Same with strawberry plants.
I use lavander, basil, chives, onions, leeks and garlic to help with pest control.
I have been told the best for deer is buying lion dung, not tried it but have been meaning to get my hands on some.
