Paul ,
Let me tell you from a very experinced person who worked the markets for a
a very long number of years now, and still does on sundays , yes myself
You would be what the market guys call "demos" and believe me if your good
at speeling and working a crowd you can work wonders selling your service,
but if you just stand and clean little interst will be shown.
ive seen men sell carpet cleaning products at a tenner a time simply by having the gift of the gab, a simple demo on a polyprop carpet, removing shoe polish ,ink etc,etc,etc, all from a bottle , agitated and wiped up

yes it really works

" well the punters seem to think so" :
so yes a great idea if you got the bottle " no pun intended" and the ability
to pitch your wares to a public gallery
geoff