Do I need a special tool to depress brake.

You might. If you do, you can tell because inside the caliper piston there will be a large slit in it allow you to use this tool :

http://www.zorotools.com/g/00044524/k-G2644835?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw= keyword &gclid=CNGklpLLrbYCFZFaMgodgGcAiQ.

(just copy and paste into your browser)

to turn the pistons back in. Please do not try to force them back in if they do not easily go back in. You could damage the brakes.

It is easy to line up the cube in the piston and you can use a ratchet to screw the pistons back in.