Best way to clean a PG 500?

For the exterior, heavy duty oven cleaner works good - wear proper ppe...

For the interior, if you just have that flaky soot stuff just use a stiff brush.  For greasy buildup at the bottom right of the unit, use a putty knife to scrape the stuff into a waste bucket and discard.

Once you get the big goop, take a shop vac and suck up the crud you knocked loose and the ash.  Suck the ash out of the fire box.  Dump both drawers.  Hopefully you lined the drip tray and drawers with foil?  If not scrape it all down and wash with soapy water.  Cover with heavy duty foil, reassemble and you are back in business.

Some time ago this question was asked and it was suggested to use:

Member's Mark Commercial Oven, Grill and Fryer Cleaner by Ecolab.

I've tried it and it is great.

I agree that stuff works! Bought a two-pack at Sam's, and I use it on the interior parts of my weber gas grill. Burned-on grease just pops off. Don't get any on you!

Spray Nine works very well. Spray on and wipe off.

I buy it at Advance Auto.

Thanks guys!

Today I dug out my old weber charcoal kettle grill that I haven't used in two years. I recalled that the cooking grate was only used a few times since new, so I heavily treated it with the Members Mark oven cleaner mountainman recommended above. Sprayed it on bricks in my gravel driveway and let it sit, a few minutes at a time and then flipped and did the other side. Used a scotchbrite pad and chemical gloves to scrub it, and it looks new! This stuff is great, but it is so caustic that extreme caution is warranted.

thanks for sharing I was looking for the same from long time.

I recently cleaned my very dirty SM066.  I used Dawn Power Wash.  I had to go over some of heavy stuff a couple of times but it did a good job.