I suspect it is a rule of life that if you don't want a green bathroom sponge then the things are everywhere. Local supermarkets offer special deals for bulk purchases of them, small children try and sell them to you through your car window (I'm guessing here, I haven't driven in 20 years), charities give them away to needy and deserving people. But as I actually did want one, there were none to be found in the neighbourhood. My original plans thwarted by the negligence of local shopkeepers, I resorted to using that kitchen essential: the pan scourer. A pack of three 4"x 6" pads, costing 49p, provided enough material to cover three of my monster-sized trees.
The scourers were chopped up into small cubes. The first of these were pushed onto the bare metal wire remaining at the tips of each bough, the wires being coated with PVA to provide a permanent bond. Other cube could then dunked into PVA and pushed onto cubes that were already in place, being held there by their tangled fibres until the PVA dried. Given the small size of the cubes (due to pan scourers being rather thin) this had to be repeated in a lot of stages, taking rather more time than I'd prefer.
Once happy with the amount of foliage added, it was pruned with a pair of nail scissors to try and remove the more visible corners of the cubes and thus give a more natural effect. The final step was brush on some light green paint to soften the deep green colour of the original pad. The net result of all this is shown in the photo.