A good question, and one which I have managed to solve after many ruined points........
I have found that, depending on the type of ballast used, and I use granulated granite, that if the point is allowed to set in position the ballast can be brushed into position using a ladies make up brush (mine was stolen from the ex), the moving parts should then be moved back and forth several times to ensure free movement. once this is established GENTLY dribble the famous 50/50 pva & water mix onto the ballast, again making sure that all moving parts do!
Any small obstructions can then, when everything has dried out, be removed with a small file or craft knife.
Hope this helps
Regards
John