Keep some facial blotting papers in your handbag and just blot it off when you can feel yourself shining up again! try not to touch your face with your fingers when out and about if they aren't freshly washed as this can add to the grimy build up on the surface. I'd also go and ask a specialist what would be the best face care routine would be for you. perhaps your skin is dehydrated and is trying to over-compensate with all the oil!
Rimmel do a fantastic anti shine face powder you can use on your tzone or nose. Ive been using it since I was in school and though I now use more expensive skincare ranges since Im working, I havent found a product to beat it yet