Fred,
I use the flex coat "lite" it is thinner and lays down better. I haven't bought any in a long time maybe 5 years, I would get it at Cabelas or Bass Pro. I need to buy some now and noticed that they do not carry it anymore
But, I just found out my wife purchased some for me at Amazon she got free shipping. My guess as far as amount would be....to coat one avg. wide bow back would be about 1 oz. I only mix enough to do one coat at a time. The work time is about 1 hour so you have to flip the bow from belly to back about every ten minutes for and even cure. Make sure before you start that you have a way to do that. As far as shelf life I've had it over five years with no problems. I believe you can buy it in 2, 4 and 8oz amounts. I generally buy 4oz at a time except this time I did 8 do to availability and I'm wanting to do about 4 bows in the next year or so with it. I glue down the feathers with it using a very soft hair brush. Do not brush the feather much, if the vanes break apart they stay apart and let the back show through and not look as good IMO.
Good luck and post your results and any other questions, I'll do my best to answer.
Bill