check the method you're using is correct. if there is zero resistance in the lever, then have you rebuilt the calipers correctly and used new piston seals? are the seals between the caliper halves correctly installed? If in doubt, just split the caliper (I assume they are of the spilt-able type) and clean everything up.
for the bleeding, are you closing the bleed valve when releasing the brake lever? a few pumps on the lever, open bleed valve, close bleed valve, release lever, repeat. Is the hose connected to the bleed valve in liquid (brake fluid) so as to prevent air being sucked back into the caliper end of the brake system?
when you've tried bleeding the system, does the fluid in the reservoir disappear? If so, then just keep topping it up, and keep going. eventually the system will fill up and fluid will start coming out at the caliper end bleed valve.