The responses have been correct--laser is definitely your best bet.
We do it all the time. You can get 950 Pd wire from Hoover or other
metal suppliers that will work well. You do not need to use the
button from the casting.
Anyone casting the more difficult high temperature metals for the
trade should have a laser in-house and should inspect and repair any
surface pitting before shipping your casting. They should not charge
any extra for this. If you find any sub-surface pitting, don't
hesitate to return it to your casting supplier for repair or
replacement. They should pay the shipping as well as long as it is a
casting related defect.
Having said that, there are times when casting defects fall into a
gray area where one cannot be sure whether it was the design or the
casting process that was at fault. In these cases the burden for
repair or replacement should be shared. In cases where the design is
very questionable, the caster should give you a heads-up upon
receiving the wax so that everyone knows the risks ahead of time.
This kind of communication is important to protect both customer
schedules and the reputation of the caster.
TechForm Advanced Casting Technology.