Thanks BigDave for sending me the post from Ben.
My problem is that the remianing algae does not come off the pool surface at all. I was hoping there is an easier way to make chlorine reach these pores so that there will be progress when I scrub next time.

As I mentioned I did make lot of progress, whatever I could remove with my brush I removed them. And my numbers are not looking that bad (dont know why I dont use much Chlorine overnight with some black algae present still).
This is what I got yesterday evening and this morn.
FC - 8.5 (no change from last night)
pH - 7.8
TA - 150
CH - 400
CYA - 40ppm
Borate - 30ppm

As you can see I also added some Borax thinking it might help me control algae in the long term. I am ading some pics with this. Some of the spots that you see in the pic could be the shadow not the black spots. As you can see the walls and bottom are pretty clear of algae, but there still some.

pool_pic_after_sruubbing1.jpgpool_pic_after_sruubbing2.jpg