Hi Paul,  I generally use 100/1 but I admit that with some brands I've gone as high as about 67/1 (150ml/litre) but have been advised by some pro's in UK that stronger mixes can actually be less effective.  I'll see if I can get a bit more info.  I agree about not soaking the leaves but I find a steady walk with the supplied nozzle is effective.  I'd be interested in more detail about the battery operated device ?
Cheers,
Bigyin