Strip old paint

I am trying to help me dad out on an old house and garage. It has pealing white paint that has been on the house and garage 40+ years. What would be the most practical way to strip the old paint off? What kind of white paint would be best to put on it now? Method of painting? SPrayer? Brush? Roller?
It does not have to be a perfect job. Just want it covered and protected.
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