For veins I start by marking the top‑level loop on the blade. Then I slice along that loop with a cut edge that follows the vein direction, keeping the split clean. Next I lay a grid of quads from the base outwards, snapping each new quad to the existing loop. Avoid auto‑retopo; it always skews the edge flow. Keep the manifold, close the holes, and you’ll end up with a tidy, rig‑ready mesh. If anything looks off, just delete the offending face and rebuild it from scratch—there’s no shortcut worth a bad skin‑line.