I tend to buy 14-15% SH myself then depends what I'm doing just dilute it down to what I want it for.
I've just done the neighbours flags outside the front of their house as a favour. Just used 15% SH neat. No wetting the slabs beforehand and no rinsing it off afterwards either as they have never been cleaned in 50 odd years. Used a window cleaner bucket and slapped it on with a truck brush... YEHAA! Job done
Just be very careful as 15 % is nasty stuff especially if used neat