This would be an ideal question for anyone who has learnt the peek-a-boo style.
Any excercises or techniques to train your head movement such as slipping, so that it becomes more natural and is quicker....?
Is it just lots of practice or are there certain ways to practice...

I practiced it a lot lot. There are techniques I guess, like the slip bag. I usually do it after every combo I throw on the bag to get used to it.

Like Versatile said the slip bag is good, i use it while shadow boxing. I don't use the peekaboo style but i still like to move my head a lot.

You can easily make a slip bag at home, there was a video on youtube about, thats how i made the one i use here at home. Basically you fill a balloon with sand, put it in a sock, tie a rope to it and hang it up.

Yea i made my bag from that video think it was on ross training. Used baseball sock and ziploc bag.

Dont mean to thread jack, but if you have a speed bag, just unclip it, and put it on another clip you have hanging. Thats what I plan on doing.

Thats what i'm in the process of doing lol, just need to buy a screw with a hook on it to put in my ceiling.