Back pack or trolley is ideal, mix it based on how bad the jobs are.
I mix it 1/3 when pressure washing, but 1/10 on what jobs av done ( so to say soft washing ) did a job on Friday, quite a bit of cladding and some render, had no chemicals except hypo so disconnected my di bottles so I went direct to hose reels, and poured 10 litres of hypo into my tank, and job went well.
Ran water through afterwards and was back to using pure on Monday