A controversial trick that I used to normalize my porosity a bit is hair dye.
Since I cut my hair back in Dec. I've used Clairol Natural Instincts non-permanent dye in #36 Midnight Black 3 times and spaced it apart about 30 days. Then 30 days later I used a permanent dye on the 4th time I dyed my hair. I made sure the dye was a little lighter than I usually dye my hair (used Garnier Fructis permanent dye in Mahogany Brown) so that it could do some serious lifting of my cuticle. I sat under a hooded dryer for 15 minutes with a plastic cap with the dye on my hair. After that I let it sit on for 15 more minutes. I rinsed it all out with warm water until it ran clear. I then applied Giovanni Nutrafix Hair Reconstructor and left it on for 10 minutes. and rinsed. It's a protein conditioner that works EXTREMELY well. It's my favorite protein treatment for a quick treatment. And then I did a deep treatment with Garnier Fructis Triple Nutrition Conditioner mixed with some jojoba oil.. The results: This color DID NOT lighten my hair very much at all. Instead of jet black hair my hair turned an off black. It looked really rich and shiny. My hair porosity has normalized now and I find that my hair accepts moisture better and doesn't feel super dry anymore. My curls look very plump, clumped, and moist. And best of all my hair is soft. Now, It still does take bit for heavy products to absorb (that's how I know it still leans low porosity) and if I use too much I have to towel blot some of it out but after I do that it's no problem. My hair is moisturized, does not dry hard or crispy, and it has bounce and movement. That is as far as I'm going with any permanent dye. Now I ONLY use non-permanet dye..my normal Natural Instincts dye in the black.
I say this way is controversial because you really have to know what you are doing and you have to make sure you use dye that isn't too much lighter than your hair because serious damage can occur. That is why I only went a shade or two up from the color I usually dye my hair. Furthermore, after you do this.. you have to be diligent with hair care. I am extremely diligent with my hair care and take very good care of my hair with no exceptions. So if you aren't going to do that period..then I'd HIGHLY advise not to go the dye route. And stick with the baking soda treatments, the castile soap, heat, warm water, and using water based products that contain emollients to help with low porosity issues.
Also do your own research. You know your own hair better than me. I'm just sharing what worked extremely well for me and continues to work.
I hope this helped. I know it was a lot but I love natural hair and I love to help people with natural hair in anyway I can. If you have any questions.. I'll do what I can to help and hopefully others come in to explain what works for their low porosity hair as well.