is a flamethrower good for moss too would you know (on asphalt)? I've not
found an efficient chemical and my back is getting too old to scrape the
stuff away every year

I don't fancy a karcher, can't bring myself to use all that water

ta

A Karcher. Wicked, will take minutes. Set it to fine jet and apply it at a
distance of nothing from the root. It will drill holes in concrete, let
alone moving the odd weed. The other option is a flamethrower, which I
used on a couple of stubborn ones :-) (actually sycamore trees growing in
the cracks)

They are very cheap from garden centres, just one little bottle of gas and
the job's done.