So, I’m fairly new to this also, but a friend at work who does miniatures and some models suggested to me to get a ‘wet palette’. I do paint with acrylic as well.
This thing has totally changed painting for me. Basically it’s a sponge on with some parchment paper on top. You put the paint/mix in there and it stays moist for days or more. Follow the directions, pretty easy to figure out with them.
But in the process, the edges of the dabs of paint will become spmewhat dry after a day or two and work out well for me for dry brushing. I picked up a wet palette at Michael’s for $15, can find them on Amazon as well.
https://www.amazon.com/Sta-Wet-Palette-Keeps-Paints-Airtight/dp/B000C18GTE/ref=sr_1_fkmrnull_11?keywords=wet+palette+masterson+8+1%2F2+7&qid=1550076644&s=gateway&sr=8-11-fkmrnull
As far as keeping consistency in color and viscosity - it’s a god send
- I was complaining about that and my friend at work suggested this to fix that problem. I like it because the ‘dabs’ will stay nice and fluid where there’s a good amount of paint, but dry more in areas where there’s not so much. So you can make a ‘main pile’ and then a smaller, thinner one that will start to dry out much quicker.
You will need to add a little water every other day or so and sometimes just a dab of medium to get it to flow right. Of course, maybe not if you want it to dry out some 
One other trick I use is to keep dabbing a paper towel and get some build up on the paper towel, let it sit and then use that as my paint source. If you get some globs, you can experiment with using just a touch of medium on your brush to get it to flow some.
I had many suggestions to just thin acrylics with water, but I’ve found that an acrylic medium not only helps preserve your brushes, but helps a lot with consistency and polymer bonding of the paint. There’s a video I ran across that explains if you dip the brush in the medium first and dab it out good, prior to saturating it with paint, it’ll help keep the pigments from staining the brush.
https://www.amazon.com/Liquitex-Professional-Flow-Effects-Medium/dp/B000KNPM46/ref=sr_1_8?keywords=acrylic+medium&qid=1550077126&s=gateway&sr=8-8
Plus - it’s cheap. I suspect this bottle will last me through probably 20 models.