What’s the best way to clean and grease these frame locks? (More info in comments)

So theres some dust / grit where the metal rod slides back into the lock, so it doesn’t work as smoothly as when new (obviously). 

So I was wondering, is there any easy way to clean these, and should I apply lube or grease on or inside where the rod is? I sprayed it down with soapy water, and it helped somewhat, but its still not completely smooth. 

Thanks in advance! 🙂