Concealing spellcasting, Any way to hide? Options

[Buster]

Since noticing spellcasting is a mundane ability, what ways are there to conceal your spellcasting?

P. 168 says "an observer has to notice the magician’s intense look of concentration, whispered incantations, and small gestures" and even someone staring at the spellcaster with astral perception only gets +4 to his Perception roll versus a threshold of Force-6.

Obviously if you're protected by Invisibility, no one can see you casting a spell, but what if you are in a conversation with someone and you want to toss a harmless Influence spell? Would a Mask spell or the Concealment power from a spirit hide your spellcasting? Would Con or Palming skill hits help? Are there any other ways to hide spellcasting?