Hi! First you have to set PS's Image Interpolation to Nearest Neighbor and configure the grid : set Gridline every to 1 and Subdivisions to 1.
Then append basic brushes to your brush library.
Pixel art in isometric view requires some simple rules, you can find some useful tutorial here : forum.toribash.com/showthread.…
notice that in this img, as a tribute to eBoy, some parts are taken by some of his works... but other are complitely handcrafted and this is only a part from a larger project, that I'll post soon
I hope to be useful and have fun with Pixel Art!