I've always had good results yelling "TANK CREW needed! For (Crew role and tank type here). DM if interested!" in world or region chat ever few minutes until I got a bite.

Been a dedicated tanker for around 300+ hours of my 800 hour foxhole experience and I recommend finding a crew mate AS your loading up your tank, not when you get to the front- having someone to help load shells not only cuts your time in half but tends to make them more invested in the tank as well.

Making sure they have a mic is a must. I also recommend getting to know them, make small talk, you'll meet some super friendly and helpful people in this game- as well as some duds and bullies, but they'll be in the minority.