In a properly executed crimp, there's nothing to fill.
A good ratchet crimper, like the Greenlee series, creates a solid mass of copper inside the lug. If you cut one in half with a hack saw, you'll see nothing but solid copper. Looks like a solid copper rod.
I'd post a pic, but I hate the Sailnet pic posting routine. WHY CANT THEY FIX IT, like Cruiser's Forum or SSCA???
Anyway, adhesive heat shrink is faster and makes a good waterproof connection. The liquid stuff is very messy.