Hi Blossom
The trouble with open pores is, once you've got them, you can't get rid of them and I am speaking from experience.
Usually, if you have open pores it has been because you have had oily skin in your youth. As you "mature" the oil decreases but the open pores stay. The plus side is that your skin will most probaby mature at a decreased rate and you will look "eternally young" LOL! We wish!
Anyway to minimise your open pores regularly exfoliate (which I am a champion of anyway to encourage new skin cells coming to the surface of your skin) to smooth and even out your skin texture and also use a pore tightening face mask.
Then after skin preparation use a good skin primer as advised above, or I personally love Clarins Beauty Flash Balm to minimise pore size. Then, forget about fluid foundatins, use a top guality mineral power, a lovely lady on our site, I think her site name is Oley, recommends Lily Lilo (apologise if the name wrong) as yet I only use a chemist chain one and will order some of the quality products as soon as my purse allows!!!
Good luck with your "minimalise my pores" quest! XXX