The ancient Egyptians were very organized, even Egyptian painting was carried out within strict confines and rules - ancient Egypt thrived on control and planning.
Art projects were first well-thought out by the master craftsmen and sketched out on papyrus paper, then they added a grid-system of vertical and horizontal lines onto the papyrus. Once they had a clearly outlined composition divided into sections by the grid, they could then just scale it up to the size of the wall.
To do that correctly, they would also apply the grid-system to the wall in relation to the plan they have on paper. They would cover pieces of string in red ink and stretch it over the walls to form the lines... Once the grid on the wall was completed, it would be easy to copy the images onto it. Pretty smart, huh?
The representation of different objects and events in Egyptian art:
The Egyptians were also always depicted in their prime of life. Youthful and healthy looking, you can hardly find paintings of elderly or out of shape!
One thing I want to point out however is that the "walk like an Egyptian" pose is not historically correct. We don't have any depictions of the arms in weird angles in front of the head and behind the butt. It is fun to make fun of it though :-)
The brushes that were used were made out of reeds with chewed up ends to make a fuzzy soft side to dip in the paint. They also used bunched up plant fibers tied together. They mixed the paints by grinding and processing certain minerals and compounds, such as:
Most of the minerals used in Egyptian painting were found inside Egypt, although some had to be extracted from Sinai and other far away areas.