So I ended up printing an ABS piece for another project that turned out 
to not be needed AND happened to be a good sample piece to test the 
latex on.
You can see in the picture that one side of the piece is latex directly 
on the plastic.  The other side had some primer sprayed on there first 
(I am guilty of mixing paint types here though! The primer is an 
automotive spray primer.)
After the paint dried, I used my fingernail to scrape at it on both 
sides - see the lines at the center top.  In both cases the paint came 
away with about the same amount of effort, but it did take a little effort.
The piece is a little flexible, and I've seen no issue with the paint 
cracking while flexing.
I should note that the paint I used was a little old (about a year old 
on the 1/4 filled can) and was not the best quality.  It was cheap 
Walmart paint to begin with even.
So, results may be better with new paint and a latex primer specifically 
meant to work on plastic.  But, my tentative conclusions are that latex 
paint is an acceptable option for printed objects.
Seeing how the paint goes on though, I think latex would be better 
suited to large areas with little detail.  If there is a lot of detail, 
I think the spray paint is a better choice.  The latex seems to fill in 
the details. (makes sense when you think about the purpose of house 
paint...)
Shawn
On 13-05-21 06:35 PM, Brad Warren wrote: