I'm not sure that you can since the lubrication is partly an involuntary, stimulated response. You might try cutting down on foreplay if that is making you too excited and stimulating your lubrication.
i don't really have an answer but do have the same problem. and leaving out the foreplay just doesn't cut it. it helps for maybe the first 20 seconds of intercourse, then it is the same as if i had a full foreplay. the only thing that improved the situation a little bit was to really clamp down the vaginal muscles, which strangely is easier when you tense your chin.