2 Answers

This works but is a bit strange.  

Take your pants out to a dirt road that is muddy, dirty and filled with stones.  Place the pants on the dirt road and drive your car back and forth over the pants again and again and again to the point of  complete redundancy.  Turn the pants over and do it all again. 

Place the pants in a garbage bag, drive to a laudromat type establishment and wash the pants in a commercial washing machine.  Use 'High Test' laundry soap.

If this does not produce the required fading results ... well, you know the drill.

Have fun and enjoy those pants!

Always remember you can purchase a brand new, stone washed pair of 'Cranky Pants' at Mark's Work Warehouse for only $19.99 plus taxes!

Soak them in Javex.