Yes, you can. You would need to lightly sand down the substrate and wipe the surface clean. Apply 1 x coat of a universal undercoat – allow to dry overnight. You can then apply 2 x coats of water-based top coat, ensuring you allow adequate drying time between coats.
You can use sugar soap to clean surfaces. You would need to dilute the Dulux sugar soap powder with water to wipe down walls and surfaces.
Brush down the area to remove excess chalkiness, apply a quote of plaster primer- allow specified drying time. Thereafter a test should be conducted to establish if the problem has been resolved by wiping the surface/area with a black cloth. If you still notice chalky residue on black cloth a further coat of plaster primer may be required followed by 2 x coats of top coat.
You can use the Dulux Bathroom paint, it is excellent for walls and ceilings in a bathroom which is resistant to moisture and steam. Independent laboratory testing has shown the new mouldtec formulation protects the paint against mould for five years.
Use a dilution of water with fungi fix to wipe down the area followed by a wipe down with clean water. Allow to dry and if necessary a coat of plaster primer may be required depending on the condition of the wall after cleaning.