What I have found about card scrapers:

1. Any old burr needs to be removed, so hone the edge flat against the stone. Do both sides before doing the edge.

2. The edge must be square. Think of it like a board, it's got thickness, and that edge face must be flat and square. Any old burr must be removed. If that edge is domed at all, it won't burnish right. So I made a little fixture that's just two pieces of oak held together with screws. That way I can hold it perpendicular to a hone to properly flatten it. Or file it if need be.

3. The burnisher needs to be HARD. Like, file hard. I got a burnishing rod which is quench hardened steel, it works okay. I also bought an Accu-Burr which is carbide, it works pretty well and is a little bit more idiot proof. Even if you don't go with an Accu-Burr, if you're going shopping for a scraper burnisher I'd recommend a carbide one rather than a steel one. Consider that recommendation the opinion of Some Guy On The Internet.

Could be a couple different things. A lot of times to get a good even bur going you're going to have to polish the edge and then the face of your card by wet sanding with a fine grit. If you skip this, you might be skipping across the high spots with your burnisher.

Another problem could be that your current burnishing tool might not have enough texture. You can always grab a honing steel from the kitchen and give that a try.

On a separate note..... How do you like the diamond plates for honing? I feel like the diamond plates I've used in the past take off too much material for frequent use.