A miniature starts days before the first line. Wasli is several sheets of paper pasted together, pressed, dried, then burnished with a smooth stone until the surface is hard and faintly glossy.
That surface is what lets a wash sit thin and even, and lets a brush of only a few hairs draw a line that does not bleed. Without it, the detail people notice in a finished miniature would not hold.
I still prepare my own. It is slow, and it sets the pace for everything that follows.