Most baking recipes use either a flour or starch (for gluten free). To use liquid lecithin in baking I suggest you use this simple ratio of about 1.5% of lecithin by weight of the flour (great weight charts found here weight conversion found here).
For example, if your bread recipe calls for five cups of bread flour and one cup of bread flour weighs 120 grams then the total weight of the bread flour is 600 grams. Therefore, you would need about 1.5% of that weight in liquid lecithin. That is about 2 teaspoons which would weigh about 9 grams (1.5% of 600).
Now, if you are using a powder or granule form then you should only use about 65% of the liquid conversion. I find it easiest to start with the liquid conversion and then just multiply it by .65
200 x 1.5 x .65 = 1.95 gm
280 x .015 x .65 = 2.75 gm