First of all, when you are washing them, the only special precautions you have to take is not to get the shampoo in their eyes and noses. Of course you dont want to drop the bottle of shampoo on their head, but they dont require any special treatment. I generally pour water over their top not from a plastic cup, and pour it really slow so that it doesnt run down the front and into their face. Then I take a few drops of flea & tick shampoo and gently rub it into their top knots with your thumb and index finger. Its really no big deal, after you do it once, you'll be a pro at it.
The spray they were using was probably oil sheen, commonly used in African American hair. Dont use TOO much though because the oil will attract dust and dirt. But a quick lite spray will add shine to the feathers, so they dont appear too dry.
The brushing is to break up the wax around the new feathers underneath, and it also helps "shred" or break up the hard feathers. It adds a little extra Fluff. Use a flea comb that has really close teeth.