basic ? is.... is it as easy to bled the brakes ona car as it is on a motorcycle?

more in depth info

i had to replace the front brake pads on the X when they were well worn. In doing so i replaced them with some real thick pads reccommended for the X from autozone . To fit them in I had to push the pistons, with a vise grip on the calipers way back which in turn i had to open the brake fluid reservoir in the engine to allow the fluid to back up.

The next 3 days were fine , car braked great.

Now afer 3 weeks of not driving the car I get in and it seems as if the brakes are real spongy.

i figure i need to replace the brake fluid/ bleed the brakes.

Any other thoughts before i open this can of worms?? or use tidbits of advice before i do this?
did i do something incorrectly??