Bleeding Brakes Problem?

I installed brand new brake pads and rotors. I tried bleeding the brakes and I cant get a constant flow of brake fluid to come through the rear calipers. I get a constant flow to come out for the front. Ive tried several different ways to bleed the brakes. But I mostly tried the one in the Haynes manual. Im not sure when the last time the brake fluid was changed. I say about 3-4 years ago. Could the lines be clogged up since the fluid hasnt been changed in so long? Or do I just have that much air in the lines? Could it be possible that the calipers are seized?

Also, what do you guys think about using the Motive Power Bleeder that Performance Products sells? Does it really work?

Thanks