Can I flat tow...

j-d wrote:
Since this Silverado is 4x2, pretty clear it's NOT towable.

I hope, though, there's a step in the 4x4 setup steps to release that Parking Brake...

It's really not necessary to release the parking brake or take it out of gear to Tow a Truck. :E

Since this Silverado is 4x2, pretty clear it's NOT towable.

I hope, though, there's a step in the 4x4 setup steps to release that Parking Brake...

Here is a what I found from a manual online, you should consult your owners manual for your specific truck though to be sure. But based on what you said since it's a 4x2 not a 4x4 the answer is no.

Chevrolet Silverado Owner Manual - 2011

Dinghy Towing

Two-Wheel-Drive Vehicles

Notice:
If the vehicle is towed with all four wheels on the ground, the drivetrain components could be damaged. The repairs would not be covered by the vehicle warranty. Do not tow the vehicle with all four wheels on the ground.

Two-wheel-drive vehicles should not be towed with all four wheels on the ground. Two-wheel-drive transmissions have no provisions for internal lubrication while being towed.

Four-Wheel-Drive Vehicles
Use the following procedure to dinghy tow a four-wheel-drive vehicle:
1. Position the vehicle being towed behind the tow vehicle and shift
the transmission to P (Park).
2. Turn the engine off and firmly set the parking brake.
3. Securely attach the vehicle being towed to the tow vehicle.
4. Shift the transfer case to N (Neutral). See “Shifting into Neutral”
under Four-Wheel Drive on page 9 for the proper procedure to select the Neutral
position for the vehicle.

lj2654 wrote:
not a 2 wheel drive truck, 4 wheel drive yes

Yes, but it needs a transfer case that can be shifted into neutral.

Bill

not a 2 wheel drive truck, 4 wheel drive yes

Probably not, without expensive modifications.
Check the Owner's Manual first, then go to the REMCO website; that will tell you if a lube pump or driveshaft disconnect is available for the truck.
You will likely also need to have a towing capacity of 10,000 lbs, and a towbar to match. I'm pretty sure that truck weighs more than the 3500 or 5000 pounds most motorhome are rated to tow!