Try taking things just one beat at a time. You need to think a long time, before actually playing the notes, and if they don't come out with a difference between the hands, take it slowly and try again.
Also, you could try playing one hand as normal, and playing the other literally on the surface of the keys, without actually depressing them. This is an exaggeration of what you are trying to achieve, and with movements that require such fine motor control, you often need to start with a big difference, and gradually refine it down.
Slow practise is the most helpful thing for this, you can't go too slowly, lots and lots of mental preparation to control the differing key speeds, and lots of good listening to critically evaluate the result.
Good luck.