Filling Porosity

Does anyone have any experience with using the Pulse Arc Welder 111
to weld in small porosities. I have been casting some large medals and
although I am getting a good finish I occasionally get the odd pit and
always in an inconvenient place! I seem to remember someone mentioning
it but I cant find the message . I cant run to a laser at the moment!
(if ever)so am looking for a cheaper alternative. By the way many
thanks for all the info on casting porosity I have been working for a
sculptural foundry doing items up to about 4KG and have been helped a
great deal by you all