divide it by two and you'll have 4 of those notes to 3. boom ta-ta-ta boom (together, right, left, right, together). that's half the measure. focus on the evenness of one hand for awhile and then the other.
Well you can either try and get the sound of the polyrhythm in your head, or you can just try and squish the four into the three (or 8 into 6). Both take a lot of work, but both ways the sound ends up becomind natural, and it isn't very difficult. Same with 2 against 3...I worked on both of these in all my spare time when I couldn't do anything else...boring math class, observation driving hour, that kind of thing. Just try and get it to fit.