My Uncle, who was a cabinet maker, dipped his chisels in varnish
after
cleaning to stop rust, personally I wipe trowels with a little oil,
otherwise they go rusty if not used for a while.

For trowels etc I also use WD40, but for woodworking tools I use
beeswax polish, more like a creme really, but it does not stain the
wood the same as oil.