I use the Merkur 1904 open comb as my go to DE, and I have the HD as my reserve or second choice, also in open comb.
The open comb has a really nice thin head, and gets under the nose really good.
4 days growth?
Slant.
I go side to side using just the corner of the blade to get the few hairs that are closest to the nose. Any other way and I either can't get to them,....