It is faster to search the entire region in two day increments until you find a target (resort date to investigate further. An entire month is 27-30 searches, as a first pass. Once I find a target, I might then pick no dates and see what other dates are around it, in various rooms sizes.
The opportunistic search is virtually impossible without an extreme amount of patience. I usually give up I find it so frustrating. Thankfully, lately all my friends and family requests have been for a fixed date. In that case I just hope for a possible instant upgrade at either the 60 day window of the 20 -15 day prior window when cancellations come back. What I have done for most of my last reservations, is book something at 60 days, and periodically check for something better. Seriously start checking again in the last 5 days before cancellation period ends. Only with 15 days or less do I book the guest certificate, unless I am able to catch the instant upgrade I want at the 60 day mark.
Funny thing that is not all that different from what I used to do. It is just now the upgrade has NEVER worked for me even though there have been opportunities I see. I have even had an opportunity where I booked a smaller unit than what I had already booked, got a double upgrade to a 3 BR, and then just cancelled my 2 BR that I originally booked with the request for an upgrade.