I’ve done this a few times and usualy head out of Aberdeen heading for the Alford road (or you clould head out the North Deeside to Dinnet and over to the Strathdon Rd). Then head for Strathdon via Kildrummy, over the Lecht and onto Tomintoul. Then head for Grantown on Spey and Dava. Follow the A939, B9010, the B9090 to Cawdor, passed Croy (careful here as there’s a turning which if you miss will land you down on the A96) then head for Culloden and over the A9 into Inverness. The last section used to be straight forward but there’s now a retail shopping complex so lot’s of roundabouts and traffic etc.
Have done the A96 heading back to Aberdeen but only managed to Huntly before my guardian angel wanted a break and i turned off for Rhynie and some sanity.
Had a look at my diary (sad fecker that i am) and it’s taken me 9 hours in the dark usuing this route.