I'm also low porosity, which is made interesting by the fact that I have been regularly coloring my hair for almost 10 years now. I'm honestly not sure how much that has really affected my porosity, as it still seems quite low. In discussing this with my mom, who also started greying (and coloring) in her late teens, we agreed that for our whole lives, we have had wavy, long-time-to-dry hair that no matter how much we beat it up, people constantly tell us is "so healthy and shiny!". It also it very hard to "weigh it down" (my wave pattern stays almost exactly the same whether short or long or heavily conditioned or unconditioned). All this led to the conclusion that we are both low-porosity. My mom went through chemo and lost all her hair, and the new hair STILL behaves this way - must have some strong hair genes in there!
Anyway. After much experimentation, I have discovered that like many low porosity curlies, my hair does not appreciate much protein, and when I do use protein, it has to be keratin. So that was the first thing that totally altered the way I hunted for products.
Then I realized that my hair hates glycerin. And sorbitol. Which knocked off a bunch of other products.
Now I pretty much use only what's in my sig - for DTs I do use a mix of Suave Naturals, olive oil, and argan oil, which I apply to damp (but warm - still in the shower!) hair, then tuck it up into a shower cap, blast it with the hairdryer for a few minutes, and sleep in it overnight. My hair laughs at other "deep" treatment methods (especially ones that just last an hour or so), but the next morning most of the mixture is soaked into my hair!
I do agree with steph that low-pooing is probably a good thing for me in that I am constantly opening up the cuticle and then putting on conditioner, so it probably soaks in better that way. Everything I use on my hair while wet seems to more or else work "as advertised". Products on my dry hair look great for like 3 hours until it soaks in or rubs off (not sure which), because after around that amount of time, my hair goes back to looking like it did before the product - makes me think that I need a lot MORE product (especially moisture), but need to find a better delivery system - probably applying everything when wet/warm is the answer, but I haven't perfected that part yet!
Mod CG since 5/10, 2b/3a, med width/density, low/med porosity, greying since 18, color over grey since 21
Hair hates: non-keratin protein, glycerin, sorbitol, agave, sulfates, polyquats, co-washing (flaky scalp), maybe aloe?
Hair loves: fewer/more natural ingredients, moisture
Scalp wash: Selsun Blue naturals or reg when desperate
Low poo: Giovanni TTTT
RO: SN - Strawberry, ES
Style: HETT mousse, FSG if I make it, ??