dyeing cotton

[threepointonefour]

I have a massive skein of bernat handicrafter cotton in a natural off white type tone. I am using it to knit up little washcloths for my cousins kids as holiday gifts. I was wondering if anyone who has experience dyeing cotton yarn with tie dye kits has tried painting the dye onto knitted items rather than dip dyeing the unknitted yarn? Or, if that won't work any suggestions for dye methods that might allow me to, for example, make the duck yellow and the water blue on this?