Dave,
As John has already implied by his post, more thorough agitation is required when using micro-splitters, and a powered unit such as a Sebo Duo or Host machine make this part of the job both easier and more effective.
The cost of these machines vary enormously, but a Sebo Duo should set you back less than £200 incl delivery. Personally, its the best money i've spent this year.
It can also take some time getting used to using these products, regarding dilution rates, application quantities and not preparing too big an area prior to rinsing as there is no need for dwell time as with conventional products.
I'm sure I remember JB saying that with micro-splitters, "Less is More" and i've found that to be true.
Regards
Mark