Lots of good suggestions... and I will just agree with the good advice you have been given...

- carry more weight (like the pack with rocks... though perhaps something more 'comforatble' - my oldest son trains for hills on hills, but he fills one water bottle with water, and the other with sand...)

- grind into the wind, or try and spin but at a higher resistence...

- setting your trainer at an angle and a high resistence is def supposed to help

- spin classes do alot of heavy resistence/standing stuff, that can help...

... but ultimately, the best training for hills... is hills...

Good luck...