I suggest you concentrate on learning to float the paper on the silver solution. It is not that hard to do, it takes a steady hand and a good tray, but will give my much more consistent results.
Brushing has many variables. What brush you use, how much silver, the concentration of silver (% solution), the ambient humidity in the room and of the paper etc. etc.
Try floating. You can practice with water and food colour until you get it right.