Honestly, don't bother.
About 20 years ago I entered loads of competitions where you had to send a postcard. You can 'influence' the person deciding the winner in the way a computer can't.
For one prize I cut some cardboard into the shape of a balloon and decorated it with 'confetti' balloons etc and won a trip for two to Italy, flights, hotel and meals included and a balloon trip.
On a smaller prize, I took some black card and stuck a white label at the top to win a case of Guinness. In all I won well over a hundred prizes, but stopped when I had to apply by computer.
Keep a eye open for postal entries, there are still some around, but honestly I wouldn't bother otherwise. If you think of it - previously you had to write out a card, get a stamp, go out and post it. Most people can't be bothered, but entering from the comfort of your armchair, and costing you nothing, you get thousands entering.
One of my other prizes was a day at a craft magazine and they said that a recent competition to win an oven for baking ceramics got one entry!
Anyway good luck.