Don't know if it's too late to help but I've done bleaching on cotton twills before. If you want a splotch or tie-dye look, try this:

Thoroughly wet the garment.

Pack the wetted garment into a mop bucket. (Twist it and pack if you want a more striped effect. Get it packed in there well.

Run an empty washer of water and open the lid to await your prize.

Pour a mixture of 1 part bleach to 4 parts water into the bucket with the garment and let it sit from 30 sec to 3 or 4 min. depending on how much color you want to bleach. (Colorfast levi's take longer.)

Pull it and rinse it under faucet then put in the washer and wash it one cycle alone then another with a bit of detergent.

Dry and done.

(I know vineagar neutralizes bleach, but don't be tempted to use it to "stop" the bleaching process... it may react w/ the bleach and dyes to give you some really GHASTLY results.)