Although I love painting en-plein air using my outdoor easel/pochade box, I also take a sketchbook for reference and work will sometimes be finished off back in the studio.
I use Rosemary and Co brushes with Daler Rowney System 3 brushes. I find both types work for different stages of the work. I have also adapted a cutdown brush for outdoor work.
I use Sennelier Abstract acrylics for under painting
I use Golden Open acrylics for the finishing; their high pigmentation really suits my style of working, especially outdoors, due to their extended drying times.
My easel and outdoor set-up are all bespoke, made by me, for me.
Various studio bits and pieces are all used in the process. Again some made by me as you cannot always purchase exactly what you want in my experience.