I would not count on receiving the credit auto-applied to your folio when you check out because you aren't supposed to receive it and if a clerk looks and sees how you booked who knows policy, they won't give it to you. If it was paper coupons I'd say use them... and don't worry.

In the old days of paper certificates as a Gold I had many Priceline Opaque (name your own price) stays at Hilton properties. Back in those old times, wi-fi was a fee but it was free if you were a member. And breakfast also was to be included for being Gold. But the official policy said you had to book through Hilton to get any benefits (including wi-fi free or breakfast free).

So a couple of things, preface this by saying all such stays were US or Canada:
1. Using a Hilton-branded American Express credit card at the check in, at the point the clerk swiped that card, it automatically linked the reservation to my HH and showed I was Gold. In many cases at that point I was provided the free wi-fi password (or told to go to the main login screen and where to click/enter my credentials) and provided the free water and provided breakfast certificates.
2. Some properties followed policy and said no benefits since you booked through Priceline, however, I could always still get free wi-fi by going to the login page and just logging in with my member number.
3. If you get really lucky after giving them the Hilton-branded American Express at check in, you may get points for about 6 stays. After that time you will receive a letter from Hilton telling you to book direct and no further points/benefits will be given to you on non-direct bookings.