Thread is one of thosse questions you will get a zillion answers for. Everyone has a favorite brand and a different opinion on cotton or polyester. I tried a few things suggested by different people until I found one I liked in price range I feel comfortable paying
Many people wash things like charm packs by hand in the sink. It is a lot of work, but some feel it is worth it. I tend to not wash, but use many Color Catchers when I first was the quilt.
As with everything in quilting, (and life) there are many methods to get to the end result. Everyone has to find a method that works for them.