Try not to develop burrs / wire edges with a razor.

Since you're able to shave hair on the back of your hand, I'm guessing your bevel is set ok. That leaves a problem with the sharpening or polishing.
A light touch is extremely important for razors. I know that's been mentioned, but it's worth mentioning again. By the time you get to the 8k you should be using no pressure.
Here's a link to some experimenting I did awhile ago: http://straightrazorpalace.com/advan...sses-pics.html
The thread is about doing a high number of laps, but the important thing to note is how much pressure damages the edge. You shouldn't do as many laps as that; it was part of the experiment.
A few laps on a step lower grit will correct any damage done on a higher grit. That's why the pyramid method works.

So... At this point - assuming the entire edge is shaving hair on the back of your hand, go back to the 4k and do about 20-30 laps with NO pressure. Do the same on the 8k. The less pressure you use on the 8k, the better your edge will be.