How to weight paint more accurately I'm trying to weight paint the beak and the jaw of my bird,but I realize that I'm not able to get the result I want. Infact,when I weight paint the jaw in red and I rotate it on the X axis,it works,but the beak doesn't. When I weight paint the beak with the red color nor beak nor the jaw are colored perfectly.
I would like to know if I can weight paint only a part of the bird,not everything. For example,in edit mode,I have selected only the vertices of the beak and I have inverted the selection with CTRL + I and then I hid them because I want to weight paint only a specific section. Why I want to do this ? Because when I paint a specific region of the model in weight paint,the painting is not carefully and I paint also the borders of a region that I don't need. I don't know if I can do it in weight paint mode,so,I thought that I could do it in edit mode....check the attached video,thanks.

video
You can use face selection masking or vertex selection masking to select only vertices or faces, that You wanna paint on.This are options located on the bottom bar of 3D view port.