They both grew up in different forms of isolation: Rey being in an every-man-for-himself scavenger hellhole, Finn having his identity forcefully squashed. They're not used to kind words. But when they're together, they each discover that they really like words of encouragement, both praising the other and receiving the praise. So just lots of compliments and enthusiastic vocal appreciation of each other, whether it's sexual or just in their day-to-day lives.