I just spent yesterday doing the same thing. What I have done is saved the powder (actually finer than saw dust) from sanding the strips to fit. I then use my glue and squirt in the crack, wipe off the exterior excess with a rag and pour some of the dust in the crack. After you put in some rub your finger back and forth. This mixes the dust with the glue and also forces it down into the crack. You may need to do this two or three times rather than use a lot of glue. If you do it right, you will not be able to see the crack.