How often you use a product depends on how comfortable your skin feels about it. The instructions may say "use 2-3 per week" but if 1x is enough, then stop there. If you like using it 2x per day...well, be careful, but whatever your skin tells you, listen to it.
You cannot "shrink pores". You can make them less visible by keep them super-clean (bacteria and dead skin - OUT) and keep sloughin' off those dead skin cells and turnin' over new ones. That's all you can do.
I am having SO much fun with Vitamin C products right now. I'm fighting FREE RADICALS. It's ridiculous. I'm using philosophy's microdelivery peel (I think that's what it's called: with the jar of Vitamin C crystals and the bottle of salicylic acid gel). Then I'm using the stuff by "JASON"(?) called "instant facial" right after that (that's 2 facials in a row people...) AND MY skin is LOVING ME for it. My pores DEFINITELY look smaller.
Then there's this stuff *I* LOVE by JOEY New York "Pure Pores Blackhead Remover and Pore Minimizer Gel". TOTALLY random...received it in a swap and was like - o.k. - whatever. Tried it. LOVE IT! Warning: I think so many people hated it, and had SUCH bad rxn's to it, it may have been DC'ed - but I think these people didn't "listen" to their skin and just applied it on places they didn't need to...like where you don't have a HUGE pore issue...just my opinion. I have THE most sensitive skin and my skin and I LOVE it.
And I am digging papaya(?) enzyme masks at night - either the ones you leave on overnight (ARCONA) or rinse-off after a few minutes (H2O+). Manufacturer recommends these 1-2x per week. Ah. I do it when I need a pick-me-up. Day, night, whatever!
All of us can tell you all kinds of things in terms of brands, but in the end, it's going to be a T&E thing for you - pay attention to ingredients, the ratios/%, etc, but I it's time well-spent. Once you figure out what works/doesn't work, you don't have to say this brand or that brand, just look for the ingredients that your skin liked.
I'm a product-whore so this method works for me. Some people have their "HG's" and are very loyal. I have "HG" ingredients to which I'm loyal.
Ooh. One thing about the clay mask you're using (or any clay-based product)...they're designed to "suck" stuff outta you, which is great...in some places, but dehydrating in others. Open up those pores (a little steam does the trick,duh) and place it where you need it (like, on your nose only) and treat the rest of your face accordingly.