Sorry, I wasn't really around today, it has been an unbelievably crazy day for me!
I have personally never done anything on jean material - so I cannot give you a definite answer. My first thought is that if the jeans are cotton, I can't see why it wouldn't work. I am guessing that with the texture of the jean, it will probably not come out as smooth as on a shirt - but maybe more like it does when you do it on a canvas bag.
But you need to know I am purely guessing - I'm trying to make it an educated guess - but still a guess. I say, try it! Maybe use an older pair of jeans first - that way if it doesn't work, you're not out much.
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If you decide to try this, please come back and post how it goes. I would love to hear!