3 against 2 rhythms can be done simply by using a technique my teacher taught me
though showing you over the net won't be so easy...

basically, have your hands and clap them to these words
"nice cup of tea" - to try and make that rhythm clearer to you, there's a slight break between "nice" and "cup", then the rest of the words follow on.
both hands start on nice, then if you've got triplets in your right hand, the right hand will take cup, left hand take of, then right hand back on tea.
repeat it and you'll end up having 3 against two.
you can practise it using the piano by playing a contrary motion C scale, with one hand playing in triplets and the other in quavers, and the hands will both land on C at 3 octaves.
hope that works!