Instead of using a sponge why not use gloves?

You put on light surgical rubber gloves then woollen or cotton glove over,
then just dip your hand into the Weed killer mix, close your hand to get rid
of excess liquid, and then draw your hand over the weeds you want to kill.

Also it is better if you can treat the weeds in the evening rather than the
morning. The weed killer doesn't evaporate so fast so more is absorbed into
the weeds.

--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk