this is what i do for indoor murals:
first, please understand that my mural work i do not consider archival and do not present it, or price it as archival. there are just too many things to control that are beyond my control to achieve AND put that kind of price on AND make it affordable for the client.
the surface needs to be clean and finished with a matte surface interior paint. i normally will have the client be responsible for that although we will consult about color choice and brands.
i use an interior room paint for any colors, including white that are most predominant. the last mural i did (in a spa where it would be exposed to high humid conditions and traffic, ie. hands touching) was mainly done with white interior flat wall paint tinted with my artist colors. i will normally block in my work with the white and then in thin watered glazes, i lay the color in. i use surprisingly little paint when i work this way. i did a 78 foot set in the spring using mostly house paint, and maybe a dozen tubes of liquitex. two of the pictures can be seen on my webpage (which can be accessed through my profile, just click on my name and scroll down to the prompt for homepage).
the brushes i use are most important. i use Purdy's from Home Depot. I believe its a Home Depot brand but not sure. I have found these brushes most sturdy for withstanding the vigorous abuse they get on walls. most bristle brushes or cheap brushes fall apart, leave hairs in the work, or wear down too quickly. those i consider disposable.
i've had some luck with lukascryl's fluid colors. they are economical enough, but i just don't like the way they perform, so i prefer using liquitex or even better, golden, for all my color work. again - using it in thin glazes can put on a lot of color without costing an arm and a leg.
i seal with liquitex, although i will caution you to make sure that conditions are perfect (humidity and temperature) because i have had that product twice dry with a white film.
these are samples of my technique
(i can't get my images down to the right size to upload here, so i put the tropical mural on my homepage....its the first one. i did that one earlier last year but it is a good example of my technique.)