brake fluid change on 1993 Chevrolet S10

I have read your description of how to perform this task but my question is when you open the bleeders at the calipers in the order you perscribe do I just let gravity bleed the fluid out or should i pump the pedal

1 answer
http://repairpal.com/brake-fluid-replacement

Referring to the article, it indicates the use of a "brake bleeder" that is used to put pressure onto the hydraulic system to force the old fluid out.