I wouldn't put a waterborne anything on MDF. I'd use GARDZ first and then I could put whatever I wanted over the sealed MDF. I tend to think GARDZ is the answer to everything except weight loss and world peace. :)

So MDF always needs some sort of sealant before any latex/waterborne paint touches it?

Perhaps these directions might help. Looks like you would need to use the Extra-Bond for the first coat after an oil-based primer. You could probably use Old Fashioned Milk Paint Company's Safe Paint instead of adding Extra-Bond to the regular milk paint. The Safe Paint is self priming and adheres to previously painted surfaces better.

Here is a link that might be useful: painting instructions

Thanks, funcolors and awm03. I am waiting on my milk paint samples now - I'll try a few different techniques and see how it goes. I suppose I can always go back to regular paint if it doesn't work out...

I painted two rooms using the new self-priming Safe Paint. I think it's great. No problems with adhesion to previously painted surfaces.

Here is a link that might be useful: Safe Paint from Old Fashioned Milk Paint Co.