To fix the gaps in my dovetails, I like to make wedges from offcuts of the same board instead of using wood filler or sawdust and glue.

I like to use the cut off pieces to make my wedges for fixing the gaps. So hang on to a few of them when you are cutting your pins and tails.

I stick one of the cutoffs in my parallel clamp just to hold it while I cut the wedge.

Since the boards i'm using are 7/8" thick, I use a 3/4" chisel to make the wedge.

I place the chisel about 1/8" from the edge and angle the chisel to roughly the same angle as the dovetail cutoff piece.

Using a mallet, I lightly tap the chisel to start the cut. Since i'm chiseling end grain, it doesn't take much pressure.

After a few taps, I now have a wedge I can use to fix the gap!

If the wedge is too thick, carefully remove some of the waste from the tip of the wedge.

This is the gap I need to fix with the wedge.

Using a mallet, I tap the wedge in place to get an idea of what it's going to look like.

This wedge will work perfectly.

So then I put some glue on the wedge and tap it back in with the mallet, making sure that it's in far enough to not have any gaps once I remove the excess waste.

45 minutes later, I remove the waste using a flush cut saw.

Not bad at all!

To smooth everything out, I hit it with 120 grit on my sander just to show you guys how it will look with a little finish work.

I applied some denatured alcohol to see what it will look like with finish applied. If I had any glue left on the surface, it wouldn't soak up the alcohol and would still look dry. If thats the case, sand it some more until it's all gone. But in my case, it was good to go and looks amazing.

It's not perfect but It's good enough for me. The only thing you will see is that line showing that it's 2 separate pieces but luckily on this mahogany, it just looks like grain. And give it 6 months to darken and you wont see it at all.  

I hope this helps.