I use a wide variety of brushes. In my early work I used standard hog bristle brushes purchased from art stores. They performed adequately and I still use them for some paintings. However, late in 2017 I discovered Rosemary & Co. brushes after a recommendation from an artist friend. I ordered a set of Mongoose hair brushes which have now become my favorites. Since I paint mostly realism I'm involved in working with detail and the Mongoose brushes, although soft, seem ideally suited to my style. Of course, Rosemary & Co. make brushes using a wide variety of bristles from synthetics to all natural.
Several years ago I stopped cleaning my brushes between painting sessions. I didn't enjoy the fumes of the thinner and wanted to make an effort to reduce the toxins in my studio. I picked up an idea from Mark Carder: use a brush dip between sessions and clean brushes only when there will be long gap between uses. The brush dip is really simple - just safflower oil and oil of cloves. It smells nice and takes a week or ten days to begin stiffening. Just squeeze the paint out of the brush with a paper towel and dip liberally in the brush dip. Sometimes I leave out the squeezing part if I'm going to be painting the next day. To re-use the brush, squeeze out the brush dip and it's ready to go - soft and pliable. I store the brushes in a simple brush holder that keeps each brush on a slight angle to keep the liquid brush dip from running into the ferrule.
When I'm not going to be painting for a long stretch I clean each brush thoroughly in odorless mineral spirits then wash with water and mild dish soap. The brush must dry completely before being used again.
I work with slow drying paint. I want it to remain wet on the canvas for up to a week so I can rework areas without having to oil out dry patches. I mix my own medium using very little odorless mineral spirits (to keep the toxins down), stand oil, linseed oil, Venice turpentine and oil of cloves. The oil of cloves is an anti-oxidant and so retards the drying. There are dozens of formulae out there for medium so choose one that suits your style of work.
I work wet-in-wet. Since I want a slow drying paint I mix my own blends. Generally I use a high quality paint that can be purchased from any art supply store. I'm thinking about mixing directly from pigment but haven't worked up the courage quite yet. However, these paints are usually very thick. I remix the purchased paint with my own medium (see above) until I get a consistency that permits good coverage and flow. Each color seems to need a different amount of medium to reach the desired consistency. I like my paint to be similar to thick ketchup when I place it on my palette.
Earlier, when I was beginning to take painting seriously again, I used a wide variety of colors. I I still have containers of tubes of beautiful colors. But I don't use them much anymore. I have moved to a modified Zorn limited palette. Anders Zorn was a Swedish painter who lived from 1860-1920. Although not exclusively, he generally used a very limited palette of Yellow Ochre, Crimson, Black and Titanium White (I don't generally consider white when talking about my palette since it is a given). Black with the ochre gave muted greens and he was able to mimic the colors of nature quite well. The modified Zorn limited palette consists of Cadmium Yellow, Alizarin Crimson, Burnt Umber and Ultramarine Blue. I'm able to create any color needed with these basic pigments. The blue and umber create a wonderful black - warm or cool depending on the proportions. Greens can be quite vibrant. From time to time I will use a touch of emerald green or pthalo blue to bump up a color when absolutely necessary.