The fans are pretty much the same except you have a starter which is turned by air. It may be apu, another engine, or external cart air to spool it up. The starter is cut out about 50% N2 and the engine should spool up to idle on its own after that. A weak air source can make a hot start more likely though spinning it up to max motor (around 22% on the JT-9) before introducing fuel helps in preventing this.