(Qāḍī Aḥmad, son of Mīr-Munshī (circa A.H. 1015/A.D. 1606))
Have a read. Scroll down to p. 198 for more painterly info. Not much info on actual practical technique and methods (for that you'll need a teacher and/or practice) but there is info on the materials, some a bit questionable today but there you go! All interesting.