Mark off these horses (do not consider 2yo, 3yo races):
Top api
Top win %
Top four place %

Set yourself a consistent time close to the jump, say 2 minutes and back the two from above with the longest prices (really a form of eachway betting).

You may not make a fortune but you may not go broke either and you will have a lot of fun some days with some really good priced winners.

My best was Jedi Starfighter at 200-1 last year.