Follow the bleeding sequence in the Shop Manual (for small trucks) - furthest wheel cylinder to closest wheel cylinder.

Use/waste a lot of brake fluid cleaning/clearing/purging the system. Presumably you bleed out of a hose that has its open end in/under the waste brake fluid in a bottle?

Do you have a helper push the brake pedal during bleeding?

Brake fluid does not disappear. You either have a lot of air in the lines, or a leak somewhere?

Good luck - keep at it.