Hard to tell what they were using, but I've used a spackle that is pink on application and dries to white - the color change lets you know when it's ready to sand and paint.

Some of the areas were dry I'm sure. They were working 2 rooms away from the kitchen and everything in the kitchen was still deep red. I might try to get a pic later today. I'm mainly interested to see if it's a pro trick that I can start using when I paint. I think they were also brushing on a liquid sander to prep the or paint, seems a lot of pros do something like that to help the paint bond.

Some of the areas were dry I'm sure. They were working 2 rooms away from the kitchen and everything in the kitchen was still deep red. I might try to get a pic later today. I'm mainly interested to see if it's a pro trick that I can start using when I paint. I think they were also brushing on a liquid sander to prep the or paint, seems a lot of pros do something like that to help the paint bond.

Some use a glazing putty made for auto body work. Multiple brands, and a bit of web searching will find more info.

Was just going to say it was probably Bondo which my guy used.

All the painter's boss has to say is, "Make sure you sand the red spots."

Ah OK, bondo makes sense. Non shrinking, sandable, and dries hard. Thanks for the answers!

Bondo is a brand name but usually refers to a two part product that is used for filling large cracks/dents/damage in auto body work, and sometimes woodwork, but would not normally be used for filling nail holes. The glazing putty shown above is a different product and used to fill tiny imperfections remaining after the bondo has been sanded.

its like a tint they mix with gap filler. so that when they need to touch up they can go straight to where it is as it stands out. its also so when they start sanding they can see the high and low points to know whether it needs more sanding or filling. my painter just used it to. just gap filler and they mix in a tint.

Bondo Spot Putty