I'm going to rent a pressure cleaner to prepare a smooth stucco on
cement block house for painting. It's been several years since the
house was last painted and the surface is chalky with some areas of
peeling paint.

As someone whose experience with power tools and accessories is pretty
much limited to rare use of a 40 year old electric drill, I wonder if
there's is much of a learning curve for using a pressure cleaner.
Would 3000 psi be adequate for a job like this? Are there certain
things to do or to avoid doing to improve the chances of satisfactory
results or is it simply a matter of just starting the thing up and off
I go?

Any and all advice and suggestions are greatly appreciated.