After trying very hard to use acrylics, I am giving up. I don't know who convinced me that it can be used like oil. That should have been my first hint. "Like oil" does not sound like it is. And frankly, I gave it all I could and Acrylic is not oil... and it is not watercolours either. Just a step in between and will take many more years for it to amount to a medium that can work indoors and out.
I wasted almost a year trying to make acrylics act "Like oils" and THEY DON'T. I give up. I will use what ever supply I still have for impasto studio work and start transitioning to oils asap. For anyone about to attempt what I have done for a year. Don't. Work with a real medium and forget the plastics. They dry too fast, are pasty and sticky if you use mediums, dry far from the wet colours and all around need more work than I care to give them. I need a medium that works with me, not one that I need to pamper.
I have been using watercolours for several years and know how to work with a tough medium, but acrylics are not tough. They are an ongoing experiment. Maybe when the experiment is done and the results are published, it will be time to revisit them. For now, I will forego open and closed and high viscosity and mediums and retarders and go with watercolours and oils.