Hello there!!! Since I been having a lot of questions about this kind of work I done in the past, so I decided to make a full comment with some guidelines you can use for working whenever designing ISOMETRIC ART.NOTE: I don't work anymore doing this type of work but I can definitely guide you with some advice. Keep in mind this is just my professional experiences and some of those tips might change with your client request or project. Thanks
First I make those images HIGH RES from 4500px wide to 150 to 300 dpi for all the detailing making it much easier.
Second brushed doesn't matter I actually used the default brush settings from Photoshop and teak them here and there to achieve any particular texture or line workflow I wanted. So nothing fancy about this.
Third, keep in mind the perspective that is key of having a good overall design whenever doing ISOMETRIC art.
Forth get yourself a good grid either provided by your client or yourself.
Finally get a background color the resonates with the final color or close color you will see in the final game. Usually provided by the client.
Work hard and always look for reference, hope you find them helpful.