Poor Man’s Rasp
Get a dowel (eg. a broom handle) and cut it in 2 lengthways, glue sandpaper around this to make a poor man's rasp. The rounded side is great for shaping a hollow, and the reverse side can be used for flat surfaces.
Overcoming Wild Grain with the Plough Plane
When using plough plane in a groove, sometimes you get some contrary grain and the plane will stop cutting. Take a chisel the same size as the groove and make chops into the wood at the bottom of the groove, then retry the plane. This will pull the blade to task and take care of wild grain.
Removing Surface Nibbing
On many projects we use sandpaper between coats of finish which take down the surface nibbing (the fuzzy bits on finished wood.) Instead of using sandpaper which abrades the surface, you can lightly use a sharp card scraper across the surface to take off the surface nibbing between coats.