You are correct on the "recipe" for coming off the fast. As to the GFJ instead of OJ, I did a Liver-Flush at the end of my last Master-Cleanse so drank GFJ first and everything was fine ('course mine had a bit of Epsom in it.... hehehe - I DON'T recommend THAT! lol). I know others have even used Pineapple juice (but don't tell Pepe ... *wink, wink*).
Seriously, though, I did 3 days of juicing after my first Master-Cleanse and really enjoyed that! I continued to detox but had all the flavor my little heart desired. I highly recommend it! There's a site I posted below which proclaims the benefits of a juice fast.