How to remove paint from rendered wall

I am current getting ready to tile one of the bathrooms at my own house. The current tiles only go to half height and the rest is painted cement render with no thin/white set. I want to tile full height but am mindful that there is a number of layers of paint on the walls, being a wet environment I want to ensure good adhesion.

What will be the best way to remove the paint, there is prob only about 5sqm, I was thinking a cup shaped wire brush on the angle grinder?

Any suggestions?


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