Bondo for sure. Turpentine will take any wax off for a good bond. I did this on my Diamond that the installers royally screwed up and it's worked a charm. Beeswax is ok but I really do prefer bondo after using it.
I've never seen bondo chip out but people used to use durhams rock hard water putty and that stuff does chip out. We've jumped, did masse shots etc and it's never effected the bondo. There should be very little bondo used if you properly level and flush up your slates. RKC has a great youtube video on leveling slates with a bottle jack if you run into non flush slates. Use his superglue method to seam the slates and you will be golden regardless of which you use.