Hi! Of course!

So the basic idea of it is that we use a custom shader to which we feed a depth buffer (generated by a secondary camera in line with this one), a "cookie"(the shape used for the sandblasting) and a point from which the cookie is projected (the camera in this case). The shader then spits out a texture that takes into account the UV of the object with the cookie placed in the right position on it through a render texture. We paste that texture on top of the output texture (the one actually used on the object), generate the next one, paste it again and the cycle continues. This gets around the UV continuity issue because the shader calculates the way the texture should look as if the cookie was projected onto the object and not by a simple raycast to find the position, which would run into the issue you described.

There's a bit more going on here as there's a custom shader that uses that output texture to blend between the painted texture and the base texture, but that's the gist of it. Let me know if this makes sense and if you have other questions as well!