Sim to what Chris said... Apply weed kill now as norm explain to customer results may be limited, due to slow down of weed growth. Sell them a Maintenance package regular weed kills, add to database contact customer every 3 or 6 mths to see if they require a weed kill. Two options std kill or + residual.
As for weeds 'poking' out fine treat them when it happens, as you say thats what you need, allow them to die off, dont remove them by hand or washing, they will die down and disappear.