trickle in(to something)
1. Lit. [for a liquid] to seep or dribble into something or a place. Some of the rainwater trickled into my car through a leak. It trickled in during the night.
2. Fig. [for someone or something] to come into something or a place, a few at a time. The audience trickled into the hall little by little. They trickled in over a period of an hour or more.
See also: trickle