1. any regular old washing machine soap will work. Just make sure it has NO softeners or bleach in it. The advantage of the micro restore type of cleaners is that they are more focused chemically in cleaning out wax and polish residue, so they will do an overall better job of cleaning out the MF's completely, but the regular soap works fine. I personally wash my towels 2-3 times w/ regular soap, and then use the micro detergent in the next wash.
2. any all purpose cleaner will work just fine. pinnacle just came out with their new XMT pad cleaner spray too. it's pretty cheap and does a damn good job. It cleaned out a completely dried up pad of mine in about 35 seconds under running water

3. I use foam from my foam gun. Works better than any QD i've ever used. If you don't have a gun, well.... get one!

but ya, just some soapy water from your wash bucket will work. DP also makes a cheap clay lube product.
4. i don't know how vinegar and baking soda would clean anything. vinegar is an acid while baking soda is a base. they would neutralize each other and leave you a neutral mixture that wouldn't do much more than make the surface smell vinegary. Try picking up an all purpose cleaner product. you can pick up a gallon of the meguiar's APC for like 15 bucks which is dirt cheap and it does a good job (just don't go off and smell the fumes. the fumes are a killer if you get a good wiff

)