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A two stop over-exposure will probably give you dense but printable negatives if you use normal development. The results might be a bit more grainy, but still usable.
If the light and conditions were fairly contrasty, you could reduce the density a bit by reducing your development time by 20%. You can then make that up by increasing contrast at the printing stage.
If the original conditions were low in contrast, develop normally.
A developer like Perceptol or (to a small extent) HC-110 dil B will decrease the film sensitivity somewhat.
Are you printing optically or scanning? Dense negatives are easier to deal with if you are printing optically.