paint compatibility?

From your previous post, I'll asume you're working on Williams passenger cars? If not, this might not be the correct answer.

First I like rustoleum. It's great for single-coat toy train projects, and car parts that will never be exposed to sunlight. Other than that, use a different paint. I tried painting an engine once with semi-flat rustoleum, it was too glossy and attempted to top coat with Krylon. Instant wrinkle finish. I've learned to never try and paint over rustoleum with anything but rustoleum.

I use color place paint from Walmart, or Krylon for most of my repaints. They seem to take other brands of topcoats well. I like to use either colorplace or Krylon primer first, lightly sand/scuff, tack, and paint. Both paints dry faster than rustoleum as well, which is an extra bonus. If it's plastic, I would always prime first with the brand of paint I'm going to finish with. I once tried to paint a postwar tender with Krylon without priming, and it wrinkled just like rustoleum.

You can purchase hobby paint which will work well, also, but I've found most of it is overpriced for what it is.

Hope your project works out for you.

This isn't on the WbB car project...but I skinned the cat. It was actually so simple, i am almost offended I think of it sooner. Details to come.....

So have I, although I do mix it up if I successfully test first.  I like Rustoleum gray auto primer because it fills better than any other primer I've seen.  Tiny scratches, etc., are filled smooth.  It sands well.  I let it dry for several days - taking a long time between coats seems to improve results. 

I think paint preference is largely what you are used to. I've learned to use Rustoleum 2X rattle can paint so I can control sheen well.   Their flat black can be nearly satin if I spray it wet and close - matching well the sheen on many new locos, or weathered-bargeque-grill flat if I back off  and slow down.  I don't use Krylon anymore because it seemed to dry faster than I wanted to paint, but it's a good paint and many people get really good results.  I just paint slow and it was too fast-drying for me.

I think eventually you get backed into mixing paint - I use all Rustoleum when I can, but there is an off-brand - I don't remember the brand name but I get it at Lowe's - enamel yellow line  parking lot marker paint that is a dead ringer for UP Armor yellow.  Only good rattle can paint I can find that does match wellk, but that brand doesn't offer many other choices.  Fortunately that yellow gets on splendidly with Rustoleum primer

Mixing paint brands and/or types, takes many tests, and remaining lucky on the final try. Any number of things can go wrong. Rustoleum contains oils to protect metals. Some paints bead on oil like water on wax. Others contain solvents than are "hotter" than the cured bottom coat can withstand, causing cracking, or pinching. Paint shrinks, and flattens out as it dries. If a bottom coat is too slick, or is somehow softer than the drying top coat, the top coat can pull or slide as it dries and/or pinches (either layer) instead of flattening out.

Using very light coats, and full drying between coats helps "incompatible" paints cure right.

Im a fan of Duplicolor automotive paints (most auto-parts stores).