"Butter someone up" means "to flatter or be nice to someone in order to get something from them". Example: I’ve stopped answering my phone when Jenny calls me. She always butters me up with lots of compliments and then asks for a big favour.
“Kick in” means “to start to have an effect or to happen”. Example: I took some pills for the pain and after about half an hour I could feel them kicking in. Get our apps for learning English: learzing.com