Painting a large area of concrete block walls

[shivvy]

I would like to paint the inside of a shed to tidy it up a bit. I just need to do a quick, cheap and cheerful job. What is the best way to do it?
I have seen those paint sprayers advertised and wondered if they would be the right thing to use because I think it would take to long to do with a brush or roller. Plus I don't think I would go through as much paint.

All ideas gratefully received.

Thanks.

[shivvy]

Thanks Tony.