The Shulhan Aruch (Siman 452) rules that one may Kosher utensils for Pesah with Ha’agalah, even if they were used in the last twenty-four hours, so long as he does so before the fifth hour on Ereb Pesah. However, Maran continues (452:2) and adds that one should not dip a meat and milk utensil together into the same Ha’agalah water, if they were both used within the last twenty-four hours. The reason is that the meat and milk flavor absorbed in the spoons will be extracted in the boiling water and combine there to form a prohibited taste. If one of the utensils had a Pagum (impaired) taste, i.e. it was not used in the last day, then it is permitted to dip both utensils together. In the event one did dip both utensils together, it is permitted, B’divavad, after the fact.
-------
Technically, a non-Jew may dip the utensils in the Ha’agalah vat, as long as a knowledgeable Jew is supervising. However, the Yalkut Yosef cites the Kav Hayashar that according to the Kabbalah, when one purges his utensils of Hames, he is actually purging his soul from sin, and therefore it is preferable that he does it himself.
-------
Hacham Yishak Yosef emphasizes in Yalkut Yosef that there is no reason to be stringent and not rely on Ha’agalah. It is perfectly legitimate and restores utensils to a complete Kosher for Pesah status. Therefore, there is no reason to go out and buy new utensils for Pesah instead of Koshering the old ones.
SUMMARY
1. One should not Kosher meat and milk utensils simultaneously unless at least one of them is "Eno Ben Yomo"-hasn’t been used in twenty-four hours. If one did so, it is permitted B’divavad.
2. One should preferably dip his own vessels into the boiling water, and not use a non-Jew.
3. Koshering utensils with Ha’agalah is L’chathila.
