Step 1: I primed it all grey
Step 2: here you have 2 choices, brush or spray the body color. If you spray you need to mask off the frame rails and crossmembers, if you brush no need for that.
Step 3: paint your frame rails, and cross members Gloss Black, I know I used Flat but that was because the Truck is already gloss black and I wanted you to tell what is part of the body and what is the frame. The Real trucks are gloss black frame parts and body color floors and under the bed, I know this for a fact I've been working on a '98 Chevy W/T 4x4 with 18,000KMS on it, it's never seen the outside of our shop.
hope this helps.
Nick