Painting directly onto bricks, block-work or stucco.
The initial preparations are generally speaking the part of the work which people tend to neglect. I can not stress the importance of cleaning the surface you are working with enough. Be sure that all areas are thoroughly clean before commencing the actual paint job. Get rid of any dust and flaking old paint. Use a high-pressure washer and make sure that any old paint is scraped away.
Once you are satisfied that the surface is completely clean, you apply a special concrete primer. Concrete primers tend to be quite fast drying and should therefore be applied quickly. Furthermore, the texture is quite thick and generally speaking you need relatively large amounts in order to cover even quite small areas. Make sure to apply the primer to all areas you intend to paint. (This includes areas with any residue paint from previous works.)
Having finished priming the surface, sand the area to make sure you are working with an even surface.
Finally apply the paint starting with any small areas which you can only reach with a brush. Thereafter you can use your roller on the larger surfaces. Repeat the sanding and painting process with a minimum of two coats.
I totally agree with the fella here, you can never take too much time in wall preparation. If you skip bit of the prep work, the wall will simply look awful!
Kind regards, Alex
Plymouth, Devon, UK