I'm open to correction on this one as it must be 18 - 20 years since I used that stuff but from memory there should be a dye remover that comes with it (I used a white foam) and use compressed air to get rid of it from any flaws but don't get it on your hands as its a nightmare to get off.
There is an appropriate cleaner to remove residual penetrants/developer, if used properly any rewelding work should be problem free from contaminants left over from inspection process.