10/10
10 points to the man above......easy method that works well on most planes. Have even used this method with the same B and Q de-icer. Takes a while but you can be assured you have de-iced properly and that you even have some hold over against further frost. ( read the label ). Use your fingers to check you have got it all off and if you have a hi tail, don't just spray it over the top and hope it does the job....get a ladder.
Give your self that extra time before your flight to complete these tasks without having to rush.
Safe flying guys