I brew a lot of lagers and rarely get any VDK/diacetyl, but I do perform a D-rest. The D-rest shouldn't take more than a couple of days, but I'm sure it could vary from strain to strain. If you keep having a VDK problem, adding yeast after the fact is a band-aid approach, there is something wrong in your process. Aeration rates, pitch rates, yeast health and yeast strains all have an impact on VDK production.
I don't like diacetyl in my beer either, the problem I have is that I'm not that sensitive to it. So when I send it off to a competition I'm not 100% sure I got rid of it. So now I add ALDC at pitch to eliminate any butter aroma/flavor. I never really had much of a problem, but the ALDC adds some level of assurance that I don't have it in my beer. More Beer carries it. I can get @ 20-25 batches per bottle, which is about a years worth for me. It's a little pricey, but if it saves one beer or gets me one more medal, it's worth it.https://www.morebeer.com/products/cellarscience-aldc-enzyme.html
It's targeted toward Hazy IPA's to reduce VDK from hop creep, but many lager brewers, both pro and amateurs alike, are adding this at pitch.
EDIT: I believe it can be added post fermentation too, it just has to be mix into the beer well.