With a platinum color hair dye (usually a 12.1 or 12.11) use only the color in the tube, do not use the oxidizer.  Then, wet your hair, and massage your hair with a very small (about a dime size) amount of the dye from the tube.  The excess of red should come out immediately, but if you still feel there's too much red, you can let that set for about 5-10 minutes, no more than that.  

It should be okay for you to color your hair again in about 15 days, it's always better to wait a month though if you can, but if your hair is in good condition (deep condition once a week), 15 days should be okay.  If you add a chestnut/hazelnut color to your hair, that is already reddish, it'll probably still stay red.  I recommend you use an ash color to your hair (say you want a light golden brown 5.3 use instead a light ash brown 5.1), so it'll neutralize the red more.  Some hairstylists don't recommend you use and ash color after a golden one has already been applied because it might turn out too ashy.  I personally haven't had a problem with that since everything I put on my hair turns out reddish (even ash tones).  I suggest you try the ash first, and if you feel your hair is too ashy (which VERY rarely will happen) you can add a temporary hair dye over it with a golden hue.  Just remember that whatever color you use should be either in the same level as your current color, or darker, otherwise you won't get the result you want since color does not lighten color, you'd probably have to use a hair stripper again in that case.

Good luck and let us know how your locks turned out. ^^