I generally throw a couple ounces in the keg. It seems to take 10-14 days to get that aroma I’m after, and with the way hoppy beers get drunk in my house it lasts throughout the life of the keg. Great way to prolong that elusive aroma. For particularly hoppy beers, I do a dry hop in primary first (after it’s done and cold crashed a bit), then another one in the keg. I’m trying that with piney hops in secondary (I had a lot of trub, chose to transfer) and then citrusy hops in the keg with my current project, a 100% Brett CDA. Loved the Citra keg hop in my last IPA.