Aaron,
I mixed batches of starting soil in a 5 gallon bucket, using eyeball calibration. I believe that it was about 2/3 peat, 1/6 Pearlite and 1/6 Vermiculite. If you need for the tobacco seed radicle to be easily visible as soon as it germinates (in a germination bed), then leave out the white Pearlite and use 1/3 Vermiculite.
All the coir products come with good wishes for a healthy environment, but the ones I tried were not particularly good at growing seedlings. In other applications, where the prime goal is to improve soil texture and water retention, I suppose it would work fine. Since it does not provide the increased acidity of natural peat, it's not useful for acid-loving plants, such as blueberries and azaleas.
Bob