1. Some have used unsweetened cocoa powder, others food coloring to darken their powder/cornstarch. I’ve never tried it myself though. My doll is slightly darker than tan, but I have no issues using regular cornstarch. I use it sparingly, dabbing on one section at a time, then smoothing evenly with a large makeup brush. I do get visible streaks from time to time, but that’s easily remedied by going over the area with a barely damp cloth.
2. I have a medium tan sex doll, and apply cornstarch with a soft blush brush. It usually goes on evenly, but I smooth out the rough spots with a gentle hand rub to the irregular areas. Most of it is absorbed by day’s end, so it doesn’t remain visible for long.
3. I use regular corn starch baby powder on tan skin with no problem. There may be a very slight white appearance at first, but it fades by the next day. It looks like she put powder on, which is fine. It gives her life, like she showered up and applied powder before bed. Also, any spots just add realism by varying skin tone.