The main drawback with WFP will always be water. It is so easy to come home with a few dirty scrims, and bits of towelling sill wipes, and chuck them into the machine.
The best thing about DIY WFP is that when it goes wrong, you know how to fix it.
Tesco brushes? I love them, do a brilliant job and are very light. Still have the Vykan brushes I started with, but they're gathering dust in the garage.
Some of us are inventive by nature. In consequence of this, we do spend a lot of time pottering in the shed. I made a brilliant swivel out of a Stanley paint pad holder the other week, it even lets you adjust the swivel action. Brilliant, but you couldn't buy one.
If starting off with WFP, I would recommend you start with a back pack. No matter how sophisticated a system you finally end up with, a backpack will always earn it's keep.
There are many drawbacks with WFP, but most of them can be overcome with good organisation. Still have to carry all that water though. Dai