It's good that you're trying out so many things. After all, we only need to have one success in order to be successful.
I've spent this whole past week trying to make milk kefir, but it's actually pretty painstaking to make it correctly. The grains have to be reactivated and then even it if thickens, there's no way to really know what the bacterial content of it is.
There's another probiotic, "Prescript assist", which contains 29 strains of probiotics, the majority of which you can't find in any other probiotic. These are actually the strains I was hoping to get from the kombucha and kefir, so it makes more sense for me to just try out this product instead. If it fails, I will essentially have exhausted all possible probiotic strains.
Let me know how the kefir-making goes for you. It was a real hair-puller for me. And I wasted a good gallon of milk in the process.