[Jeffrv]

One person has suggested partially depressing and holding the brake pedal down with a stick before starting to work on it, this closed the compensating port to prevent easy flow of brake fluid as you have the system open. If you do get air in ABS, the 1995 GM manual for abs brakes suggests the followiong:
Press the pedal to bleed, open valve, close it at end of stoke, release pedal,then repeat. Bleed rearmost valve on hydraulic modulator/master cyl assembly until clear of air, then bleed front valave. Bleed wheels in right rear, left reat, right front, left front. If pedal ok, your finished, but if mushy you have air in ABS. Start engine, run 10 secs, turn off. Repeat at least 5 times. DO NOT touch brake pedal as you do this as it inhibits cycling.Each start cycle actauites and homes the valves and motors in ABS, dislodging air inside. Re-bleed system asd above.
Jeff