I would be interested to hear your technique when knocking on doors it seems a delicate subject to approach when asking a stranger if they would allow you to go on their land with an air rifle
Well it may be a bit of putting at first but stick at it
when you go try to turn up reasonably smart .be polite and if you get knocked back say thanks and leave your name and number in case things change in future.
always tell people your looking for somewhere to shoot i have just sorted some permission on a large riding school by word of mouth.sort your self insurance before you start it helps