Thanks to RagnarokBazil for the idea and battle result screen.
I suppose you already know about the South American/Australian servers. You can use them to play matches with bots and have an easier time making credits at low tiers than at higher tiers. It’s even possible to survive 100 battles in a row, since most battles with bots are basically 1v1s.
You can make tier 8 credits at tier 5 and make tier 5 credits at tier 2. That nets you 90k to 125k per battle with a premium account. With a credit booster you’re looking at 200k even. With a tier 5 premium on the ASIA server you almost always get top tier too. The bots only shoot premium ammo at tier 4 and 5; so tier 3 and below, if they can’t pen, they will shoot only HE and they can’t hurt you at all. Bots show up at only tier 1 to 5 if the player count is low. You can make 1 million credits in under 10 battles with a premium account. You can skip tiers with this tactic as tank rewards missions are counted at tiers 1 to 5.
The best tanks for doing this are Panzer V/IV, Churchill III, T-14, M4 Improved, Excelsior.