Obviously the front pairs needed more attention so I started to remove old dye using prepping agent
After a lot of wiping and sandpaper - about 50% cracks were gone at this point.
Then I grabbed crack filler
and applied it on the seat..
and sanded until I got the smooth surface
(Note: do not put excessive amount of fillers like I did, because after about 3 months of usage, deep cracks are showing because the cracks are rubbing against each other and damaging the point where I filled with the crack. If cracks are too deep to be filled, just let it be. Don't try to smooth them out)
Anyways, after about a day, I started to dye the seat with leatherique dye using brush. I don't have pictures for it because thing got very messy and i didn't have an extra hand for a camera.
here is the surface - I should've put more coats because dye in side lower bolster came off after about 5 months of using. I put about 4~5 thin coats(opposed to 2 last time) for driver seat - they still look good so far.
Before & after
I'll update you guys soon with part 2(driver's seat with torn off bolster and cuts)