Looking for a bit of advice on preparing and painting external walls. Moved into a house with painted external walls. Areas are in really bad shape with flaking paint. I have been trying to remove with non metal brush as recommended on paint container but still get what looks like rust so thought I would just use metal brush instead. I have thoroughly removed paint but have left black marks from the metal brush. Will masonry paint cover this without rust appearing through the finished paint? Any suggestions for removal and stopping rust ? Also should I prime the walls after preparation with something and if so what b should I use. Thanks
Not a particular area of specialism for me so I just add my penny's worth. Use a breathable paint. A non-breathable paint (or more of a sealant) will trap moisture in the bricks which does two things. Eventually leads to penetrating damp, and as the bricks will not breath or dry out, the damp bricks will be less thermally effective making the property colder (the spores in the bricks will be filled with water not air). This is a particular problem in old or existing buildings. This is the reason many home/building owners choose to sandblast the paint off and repair/point the brickwork.
Masonry paint can be removed with a wallpaper steamer also a hot air gun, you would be advised to not use a wire brush as the black marks you describe are metal scratches from the wire brush. Once the area has been prepared you can seal it with an oil based primer sealer such as Albany Primer sealer prior to applying the masonry paint.
I believe you would be very unlucky to have any adverse effects from the wire brush marking, see if you can remove these marks with a stiff bristle brush but don't lose any sleep over them however if they seriously bother you prime over these marks using Zinsser 123 Bullseye. With regard to masonry paint look for those that carry the BBA marking (British Board of Aggregates) as these are approved with up to 15 years longevity. Maybe if budget allows go for the 'Trade' versions and avoid the retail brands. Market leaders being Dulux Weathershield and Sandtex Masonry, go for smooth rather than textured.