One minor flub on my part was purchasing acrylics to begin with. The whole concept of being an artist had me dreaming of waling into a studio and smelling the honeys that I associate with art and ultimately oil in particular. At first all I did was pencil sketches until I got brave. I'd started with watercolour pencils only to learn that watercolours are a whole different animal and very unforgiving to a newbie. I wanted to paint like the masters and at the time it didn't occur to me to try oils. What deterred me was the news that oils aren't eco friendly and many venues don't allow it's use. Some people have become highly allergic! There are water based oils, but what the heck is that if not some form of acrylics? And where's that smell? That confused me and so I stuck with acrylics. The problem with them of course is the drying time can be a bit faster than I can paint! I have this hummingbird habit of painting in more than one place at a time. But because I have a full stock of acrylics, I'm not about to switch just yet.
Consequently the first "additive" to my tool box was retarder. After discovering dried out patches where I wanted to blend, I found it to be crucial when using acrylics. Just a small drop mixed in with the heavy body acrylics I tend to use (a whole other story), is enough to slow the drying time down sufficiently for me to move the paint around until I'm satisfied. I had tried using just water, but the paint if thinned too much won't adhere to the canvas for very long. Occasionally I can get away with a bit of water, otherwise I prefer the feel of the retarder as it gives my paint more flow without reducing the colour intensity. This is great when using rigger brushes for long hair etc..
The only minor issue I have is that the final result can show shiny spots where the retardant was used. My solution is to give the completed piece a spray coat of mat acrylic varnish to unify the surface reflection. (I prefer a mat finish so no glare obstructs the viewer from the artwork. ) You could opt for the gloss varnish too if that's your thing.
On a scale of 1 - 10 I rate this product a 9 !