A quiet room doesn’t need filling. Let the silence finish its sentence.

Silence between people reads as a problem that someone has to solve, and the person who feels it most keeps solving it. Filling it immediately means nothing gets finished, not the thought the other person was having and not the one you were. Quiet in a conversation is usually the end of a sentence rather than the end of the conversation. Letting it run stops being awkward once you have done it a few times.

Let the next pause last. Count to five in your head if you need something to do. What comes after it is often the part that was actually worth saying.