Koshering pots

When boiling and koshering pots  does the water have to boil over the sides of the pot? Or can we just bring the water to boil and spill it out? 

Pesto made before holiday

If I made pesto in my food processor that I’ve only ever used for cold food before Pesach is it ok to use on passover Ingredients I put in were fresh basil and olive oil kosher salt and black pepper  I used a plastic spatula