If you look up the FF feeding schedule for soil you will see how much of each i use during flower. I use the same amounts as the chart suggest. I would post a link for it but i dont want any infractions haha. Google or bing will take you to the schedule. But yes i use both at the same time. The first time i feed i use half strength and the following feeding i go to full strength. Usually start feeding around week 3 of flower.
As for the molasses i use either grandma's or brer rabbit molasses that you can get at wally world or a grocery store. Its by the syrup. I will usually add a tsp per gallon of water on the nonfeeding days. Just water and molasses. Check out this link when you get time. It will tell you more than i know haha Molasses is Sweet Organic Goodness