Edit Mode Tools¶
Mode: Edit Mode
Panel: Sidebar ‣ QuadGuide ‣ Selection
Remesh Selected Faces¶
Select the faces of an area that came out wrong and press Remesh Selected. Everything around it stays as it is. Seam Density makes the inside denser than its border (2 = twice as dense).
Fill Hole¶
Select an edge of a hole and press Fill Hole. A round hole gets a circle in a square; a hole with corners gets a grid.

Bridge Loops¶
Select two edge loops and press Bridge Loops to join them with quads, even when their edge counts differ. Steps at the 3D Cursor puts the count changes where the cursor is, such as between the fingers.

Fill the Rest¶
On a partial retopology, remeshes the part of the high-poly mesh it does not cover yet and joins it on. The high-poly mesh is the retopology's Shrinkwrap target.
Guide from Edges / Protect Selected Loops¶
Turn edges into guides, or keep a loop of the result in the next remesh. See Guides from a mesh.