Can you offer advice about what kind of brush or roller I should use?
The first thing you need to do is de-gloss the cabinets or no paint is going to get good adhesion. Once the prep work is done (the most important part) then it’s up to the look you want. A brush is always going to result in a brush stroke look while a roller will give you a more even finish. If you have a raised panel door you would need a brush to get into the nooks and crannies and then you could finish with a roller. A sprayer will give you the most even finish. Take the handles off the doors and string them up through the handle hole. Then spray. This will give you the best look (just be careful the spray paint doesn’t run).