I would use an odour digester there are loads around perhaps try Prochem but in addition you could HWE then put said product (IMO I don't think Mpower would work - no politics!) then leave some dry granule dry cleaning powder like Host pushed and brushed in and advice customer the vac up 24 hrs later.
Sour milk has an enzyme and a product like Microsan will brake it down but there are loads of others.
Shaun
Ian did you get my PM on c'talk?