They're easy to use.

Just book your hotels like normal - with your credit card.

Then, at any time during your stay, hand over the gift card(s) you want applied to your bill. You don't need to use the restaurant, etc.

No need to book anything differently or inform the hotel in advance of your intent to use a gift card. They're like cash.

...unless you have some weird kind of gift card that has other restrictions on it...

(Obviously limitations apply: you can't use them for prepaid stays, third-party-paid stays, Priceline, etc. And you can't turn them into points to use for awards. But your typical run-of-the-mill booking where you pay the hotel at check-out, no problem...)