I just nv4500 swapped my 98 k1500, I used a 95 transmission with the external slave. This is the method I used with great results:
Remove the slave cylinder from the transmission.
Reinstall the plastic retainer onto the slave cylinder.
Fill the master. Tap the side of the master with a small hammer or screwdriver, it will start forcing air out of the system, refill as necessary.
Once all bubbles are gone, have a helper go under the truck and actuate the slave in and out. More air will come out of the system, again refill as necessary. Once all bubbles are gone the system is bled. Install the slave and you're good to go.
No messing with a finicky bleeder and quicker too!