60fps/30fps slomo

I'm currently working with a 30fps timeline and would like to add a few 60fps clips for slomo. I don't want the entire 60fps clip to be slomo but only a small part of the clip. This leaves the rest of the 60fps clip looking sped up, jumping, unnatural. Is there anything I can do to get the clips looking uniform?

Secondly I'm trying to create a demo reel and have both 60fps and 30fps clips. I set the sequence settings to 60fps for the timeline but I can still tell a big difference in the 30fps and 60fps clips. Is there anything that can be done to make everything look uniform?

I started shooting in 60fps and using 60fps timeline hoping to get rid of the problem above but the 60fps footage still looks unnatural and slightly sped up. Is there something I'm doing wrong?

1 - Select a Range of that clip, Command-R brings up its retiming header. Select a speed there, only the Range will be effected adjust as needed. Or slow the whole thing down with eh Conform command, then use a Range to speed back up the other sections.

2- Create a 30fps timeline to edit in.

3- What camera are you using?