Pore filling with chalk

I gave up looking for finely ground pumice and settled for chalk. I did some experiments recently on the walnut tenor (which sadly seems to be lost in transit near Ipswich) and now I'm turning my attention to the little koa soprano I'm making. 

It had two wash coats of amber shellac a few days back, enough for me to see the pores. I was a bit braver than last time, I simply used the muneca almost dry to smear the chalk out. 

As you can see the back turned dull and greyish. I kept rubbing for a while, using the chalk as an abrasive. Then when I had chalk powder in the pores I brushed off the edges (where a lot of powder had gathered) and loaded the muneca with shellac. 

And wiped down the back. Then I did the sides and the top. Much trickier, the sides are curved and the top has both the bridge and the fingerboard extension blocking the way. But here's a pic of the back. I might repeat the process but actually most of the pores seem to be filled already.