Refinishing a hardwood door

I am currently refinishing a hardwood front entry door; oak,
I think.

I have just about completely removed the old poly and stain
by sanding. However, in a few areas, the surface wood is
just a tiny bit softer and more fibrous. I assume this is
due to some moisture penetration under the old poly.

These areas are still pretty solid -- can't dent with a
thumbnail. But I can see and feel a subtle difference when
sanding them -- the dust is courser, softer and more fibrous.
In the sounder areas the dust is fine, dry and powdery.

What can I do with these areas prior to painting with fresh
(oil based) poly? I don't think sanding all of the slightly
soft material away is going to be practical.

I have seen various "wood hardener" products in the big box
stores but have never used them. Are they appropriate here
and do they work? Some other treatment?

FWIW, this door is fairly well sheltered under a deep
entry porch. I am not planning to apply any stain.

--
|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
| Malcolm Hoar "The more I practice, the luckier I get". |
| [email protected] Gary Player. |
| http://www.malch.com/ Shpx gur PQN. |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~