'02 silverado rear brakes

Even though it is the correct way?

The idea behind it is simple. The dirt and crud in the system flows down stream. Water, rust and rubber all settle out of the fluid. When you push the pistons in all of that crap can be pushed up through the lines and back into the ABS unit. If you look at 99% of the service manuals they will tell you to open a bleeder and push the fluid out. Then you just top up the fluid with new. Easy enough to do and unless you release the pressure on the clamp without tightening the bleeder first the chances of getting air into the system are really slim.

Gee, thanx for that wonderful explanation!

Shouldn't matter cause the brake fluid should be clean, cause "you" change it every 12 to 24 months, 25K, 30K or 36K since "you" follow the "service manuals" !!!

I didn't say it was.

You might want to look in those manuals. Most of them don't even spec brake fluid changes any longer. Do what you want but I would rather not screw up the ABS unit on customer vehicles by not following a very simple procedure.

One more question, some pad brands contain new stainless steel sliders and other have none. Is it necessary to use the sliders or can the pads be held in place with just the caliper bracket?

Those are actually anti-rattle clips. They keep the pads from dancing around when you're not using the brakes. Without them you get clunks and rattles when you hit bumps.