Corny for secondary?

I've got my first batch fermenting and it smells great, I can hardly wait. I've got a few questions just like every other newby. The first day in the ferment the airlock was bubbling like mad. Day 2 was one bubble every couple of minutes and day three no bubbles. I guess I should mention I made an English brown ale from a kit. I was expecting a longer fermentation. Nothing to worry about right? Just wait for the Krausen to fall?

Also, I've been reading alot about secondary fermentors. A friend gave me some corny kegs and I don't have immediate plans for them. Could I use one of them as a secondary? Will I still need to put an airlock on it? Thanks for the help.

First off, I don't keg yet....but

When you transfer from the primary to the secondary, I have found that you have a tendency to stir up the trub a tiny amount and re-activate the yeast a little bit.
Almost everytime that I have done this, I get a minor amount of activity in my airlock on the secondary. Then, after a few days, things continue to settle out and "conditioning" continues. I have a few 5gal glass carboys, they were not terribly expensive.

You could try, maybe leave it in the primary a bit longer than necessary to settle out the brew even more before you transfer to your corny.

I've used a corny as a secondary in a pinch because it took up less room in my fermenter refridge. Just burped the valve occasionally.

I use them most of the time. I put a gage on a gas connector, so I can watch the pressure. Even if you don't burb them, they relieve at 130 psi.