Can't get brake fluid from abs into lines after installing new brake line on a 2000 chevy silverado

I read this same problem all the time, the reason u can't bleed the lines is that a special tool is required that pluge into the ABS and holds the hydraulic valves in the ABS control open for bleeding, there is no way around this.

What is tool mentioned and how does it work for bleeding ABS brakes on a 2000 chevy silvarado

Under the firewall on the drivers side is a proportioning valve which may need to return to center before you can bleed the system.Get someone to put the break pedal down why you tap on it and the continue tapping on it with the brakes being pumped up and down and it should find it's center.When it does free up you should be able to bleed the system.