You're probably talking about this knife:
I do it just like everyone else is saying, by using files. It's safer, but the main reason is because I can control how much material, wood or metal, that I am taking away with a file rather than using a grinder.
First I like my grooves to look a certain way, so I using a magic marker to draw out how I want my lines to look.
When I start filing, I use a normal Nicholson file. I prefer the metal ones, even though I'm carving wood, I just like the metal ones better. I tried using wood files, but they took off too much and that is probably because of my lack of skill more than anything else. I use this file to establish my depth and make the foundation for my carving.
If I have curves, like with my Twisted Fighter, then I use smaller flexible needle files. I use their flexibility to cut the waves or curves in my grooves. Once I'm satisfied with the way the handle looks I clean up all of my file marks with sanding paper. Working my way up from 30 or 60 grit to 400+, depending on how I want it to look.
That's how I do it. I try to keep things as simple as possible. I hope this helps.
Logan Pearce