The loctite 420 is so thin that it will wick into cracks that are nearly invisible, so yes, it should do the job. I would use an insulin syringe with the smallest needle that is available.
I was repairing a crack similar to what you describe a few months ago. I would lay a thin layer on the crack and it would draw into the wood almost immediately. It probably took me twenty minutes of repeated applications to fill the crack.
Using a really fine needle makes finish touch up quite easy. The super glues are a great thing to have for repair but keeping them off of the finish is worth some extra effort. That is, unless you are doing a full finish restore. I try not to over do the glue. Just fill the hole or crack until it is level and you won't have to scrape the excess off. A light sanding with some wet 320 or even 600 grit followed by a couple of passes of truoil or poly on a tight woven piece of cotton cloth will finish the job.