I think you'll get varied answers here, burning with a harder grade filter may do the trick for you, likewise using a softer filter for the opposite reason. My enlarger makes it difficult to change filters without disturbing the enlarger, so holding the filter beneath the lens might be an option, or placing a filter over the opening of your burning tool. Also remember that before VC paper came along this technique wasn't possible.
The filter trick is a good one, but maybe now it's time to start playing with potassium ferricyanide, or ferry as it's affectionately referred to. This is a print bleach that eats silver density. The density loss effects all areas equally, but is much more noticeable in the highlights as, obviously, this is the area of least density. You may even find it useful in addition to split grade printing.
There are two separate methods. One is to apply a solution of ferry till just before you see the tone you want, quick rinse, and drop in hypo. The hypo, or sodium thiosulfate, neutralizes the ferry and stops the bleaching action. The print is then ready for archival processing. The second method involves a solution know, under Kodak's proprietary name, as Farmers Reducer, and is available prepackaged from Kodak. It' a FRESH made solution of potassium ferricyanide and sodium thiosulfate together, though you still bleach-hypo-wash, as above. The advantage(?) is that WYSIWYG, the disadvantage(!) is that if you go too far with this bleach the density is gone forever, ie, you make another print. Farmers reducer must be used immediately, because while the hypo in the solution is removing silver, hence the WYSIWYG, it's also neutralizing the ferry, becoming less and less effective.
If you use your ferry separate from the hypo, as I think most people do, you have the major advantage of redeveloping lost density if desired.
Sounds like magic right?
Have fun!