If this is a water prone area, you don't want to put the tile over drywall, but rather over durarock or other cement board product. If any water should get behind your tile onto the drywall and compound, your tiles will come off.

If it is a dry area, then drywall and joint compound is fine and you should prime the area before tiling. Painting is not needed.

"If this is a water prone area, you don't want to put the tile over drywall, "

No place in a residential kitchen is a wet area.

Wet areas are around tubs and showers, not residential kitchens.

Thanks, I think the area is truly just a "splash" area. We chose not to have the counter top built with a splash guard, as was the case for the old top. We plan to run tile down to the counter top and use caulk at the interface... and grout sealer. The area behind the faucet does get splashed, but not wet like a bath tub or shower area.

The main concern I wished to express in my post was a concern about drywall patches and the quick set (mud) used to mount the tile. The mud has to dry without pulling out the underneath patch material. So, it seemed like painting over the patched area would be best... maybe necessary.

The absolute easiest way to prep for your tile will be to yank out the old drywall and install new. All you will be dealing with will be the seams then. No patching holes and dealing with gouges and other problems. But another view to that would be to go ahead and install the cement board. It will need minimal seam attention compared to drywall and it is sturdier and will provide a flatter surface onto which to install your tile. And, the larger the tile you intend to use, the flatter the surface underneath will need to be.

Kitchens are one of the places you can get away with mastic to attach tile.

You are not going to get enough water on a back-splash to make it through the grout joints unless you are flooding the kitchen.

The grout joints are the 'weak spot' for water penetration.

Repeated wetting (like a shower enclosure or tub surround) can allow enough water through the grout to start problems.

Even in a wet location, an additional barrier is used to prevent water from moving through the grout, the thin-set, the backer board, and into the studs.

You need to be very clear that 'waterproof' often means water does not damage the material, NOT that it stops water fro passing through.

While cement board is 'waterproof' is is a cement product and wicks water (like grout) very nicely.

Thanks, it isn't just terminology? I've been calling the "glue": quick-set and mud. Is Mastic another name, or is it different? If different, is it easier to work with, "quick grab" and good working times?

Mastic works better directly on drywall.

Thins set is a Portland cement product and if the water soaks into the drywall quickly the Portland may never have a chance to cure.

It does NOT cure by drying out, but by hydrating and chemically incorporating the water used to mix the powder.

Mastic does cure by drying out (more or less) so it is not really harmed if some of the solvents move into the drywall quickly.

Thanks, sounds like the mastic may be a good choice. I do not expect the back splash to get wet, but behind the sink ... not so sure.

The word "solvent", as in mastic, makes me worry about getting any of it on the new acrylic solid counter top. I know I couldn't use plumber's putty to mount the faucet as it will stain the acrylic (marble, etc.) due to the solvent, not water based I assume. Yes, I would clean any off a soon as I found it...but hope to clean with soap and water only.

"I do not expect the back splash to get wet, but behind the sink ... not so sure. "

Are you planning on using a sprayer to clean it?

It is NOT going to get wet enough to matter.

Cover the entire counter with multiple layers of newspaper held down with blue painter's tap.
Then put a decent canvass drop cloth on top of the paper.

Mastic can damage synthetic counters.