Reddit reviews The Natural Plaster Book: Earth, Lime, and Gypsum Plasters for Natural Homes (Natural Building Series)

I've removed this thread as this is all pretty broad, easy to find, hard to answer in a comment, or covered here plenty of times before.

> What loop/sample sites offer free samples/loops

You can find this with search

> What is the best way to fill in the buildup?

Listen to tracks you like and do what they do

> Anything to take into account with vocoders and vocaloids?

Learn how they work and where vocals sit in a mix

> Is there anything I should know about mixing&plastering as well?

There are entire books about this, such as this and this and this ;)

You're welcome to post all of these in our regular "there are no stupid questions" threads; there should be a new one today. Best of luck and don't be afraid to research and just try things!