I decided not to use Homasote and just used a vinyl roadbed called Flexxbed made by Hobby Inovations. Here is a picture of what it looks like going down:
The Flexxbed is easy to install and I am very happy with the noise level. The main reason I didn't use Homasote is because of the time and difficulty involved in cutting all the pieces for my layout. Most of my layout is open grid benchwork, so I would have had to do a lot of cutting. Here is a picture of a finished section of the layout so you can see what it looks like with ballast.
