You may want to grind/machine out those pits before you try again to get rid of any crud left over from the previous attempt. Maybe clean between laying beads. If you have an O/A torch as turbo38t said you can use silver solder. I like Handy Flux from Handy and Harman for this but to get a complete cover it has to be clean. Or you can use bronze but it also requires complete cleanliness.