Frei is an excellent source for gravers. With most of the trades going with air assisted tools and small square shanked tool bits, the traditional tools are harder to find.
Even Brownells and the like used to have a couple of pages of just gravers for sale. That's long gone.
Use a light cut with a liner in shading. You only want the individual lines to be cut, not deep enough to engage the front edge of the tool itself.
That technique can be used in background removal where you want to remove metal deeply, evenly and leave the surface lined as well.
If you cut too deep while shading and dig the tool face in, it'll show up glaringly as something other than a row of fine shadeing cuts
There's no heal on the tool, just the face angle, so it doesn't like to go around corners well. The light cuts are again in order to avoid digging a furrow behind the tool as you turn.
No heal also means a weaker point.
Use it by hand or with a hammer.
Try the 'bent' liner tools for hand graver work if you get a chance. I find them more comfortable for that. Everyone is different though and the simple straight shank tools may do just as well. The straight shank liners for hammer work .
Quite commonly used in jewelry work, a bit less so in gun work but still common to see.
Liners can be rolled into and out of the work to mimic the variance of start and stop lines of single cut shading. The always perfectly parallel lines give it away as liner work, but it does look nice when well handled.
'Best' quality work is single line cut shading. But in restoration or strict replications, you use what the piece demands.
Some practice, a light touch and you'll be on your way.