Weedol 2 was a contact weedkiller so it worked fast on contact with the green leaves, but it was not moved through the plant to the weeds roots. Perennial weeds would most likely grow back and require further treatments.
Weedol RootKill Plus is available and does take longer to work, but it will kill right down to the roots. Weedol Fast Acting Weedkiller is a new Contact weedkiller so will be fast but best for annual weeds as it likely won't kill the roots of perennials on the first application.
Weedol Rootkill Plus needs 6 hours of dry weather. Weedol Fast Acting is quickly rain-fast... pets can go into treated areas once the product has dried.