Is it advisable to paint brick?

I would have no hesitation about painting brick. You would need to clean it well first. Your paint supplier will be able to suggest the cleaner and paint to use. If it's located somewhere you could use a sprayer, that would be my tool of choice. You can either buy or rent one.

Inside or outside as they are two different methods

there is special paint for brick and yes, I just passed a McDonalds being painted grey over red and white. The man was using a brush to push the paint into every nook and cranny. There must be a better way!

You should be able to without a problem.

Normally I would say I'm against it as you will always have to paint again. With your add-on's being different colored brick and the mortar also different colors, I'd say yes - go ahead - your house will have a more cohesive look. Remember, brick is porous and will take a lot more paint than you think.

I personally prefer brick stains, since where I live painted brick does not fare well, and is high maintenance due to peeling. I guess it depends where you live. If you see a brick house in your area, that is well painted and holding up, ask the people what they did...lol.

Stains are breathable, so they are less likely to peel due to water damage. People either don't stain the mortar for a more natural look, or use a different stain.

Here are a couple of brands among others.

http://permatint.com/

http://www.dyebrick.com/