Sun straight up in the sky you just don't want to even try.
Might could try a couple of things though. First; SHADE. Next; if you have a canopy that you can block direct sun from hitting the area you're trying to photograph, and the sun is at a steep enough angle to still bounce off the surface. Finally; you could try a large umbrella to do the same thing, IE shade the direct area and have the sun coming in from an angle.
What is happening is your camera is seeing a ton of light and shutting down the iris as well as speeding up the shutter speed. (IF and only if you have at least a point and shoot. Phone cameras do some of this, but its all in the software.)
If you get a decent little DSLR you can set it in aperture mode and it'll adjust the shutter speed automatically. You can play with the aperture (F stop) and try and close it down. With F stop settings the lower the setting the bigger the opening for light to get to the focal plane (film) (pixel thingy).

In bright sun you just set it at say f22.
Or, you can put it in timed mode (shutter mode) and as you slow down the shutter, the aperture will open up, and as you speed up the shutter the aperture will close down.
Best thing would be go fully manual. Now you've got the ability to both close down the aperture AND seriously speed up the shutter speed.
With any of the above modes you would also want to back off on the exposure mode. If your camera has a meter that tells you it's at the right exposure mode, and you're in bright sunlight (trying to capture too much light) then back off on the exposure. There may be a setting, -2, -1, 0, +1, +2 like that. Start with -1 and take a shot, the -2, and so on.
Basically you want to UNDER EXPOSE your shot. In normal situations the entire thing would be dark, but if you're really wanting to get this type of shot you can really under expose the shot, either by clamping down on the aperture, running the shutter speed up, under exposing the shot OR a combo of all three.
Finally... some DSLR's have the ability to "bracket" a set of shots. You can tell it how many shots to take when you push the shutter button and where to place those brackets. IOW's you can start it at -4, then -3, -2, -1 or something like -2, -1, 0, +1, +2.
(Also fwiw some cameras don't do FULL exposure settings but can actually do 1/3rd, or 1/2 settings.) Those however are more for normal shooting and very fine work. Shooting sun reflecting in paint I'd do at least full stops.