About the only thing I found is to slow the car without putting on your brakelights. A little e-brake, drop it out of overdrive or just come off the gas going uphill. I want them to feel like they are about to run over me. Most people have no sense of speed or relative speed, so they get confused whether you slowed or they ran up on you. Not like when you brake check them, they see red, red MAD! Usually they will go around once you do that once.
That applies if you are in the correct lane for your speed and there are passing options. Occasionally I have been able to blink the hazards and they understand. More often than not, that is just an invitation for them to be asinine. If you are not in the correct lane, get there! My favorite sign on a highway is "Slower traffic Keep Right" If I am on an interstate I will probably keep it in range of 70-90mph depending on traffic, cops, and such. Not really a constant speed type, I take what I can get. On an 8-12 hour trip my average speed is 65-70. Counting the rest stops, gas stops and such, that means I get moving when I am on the road. Point is, I don't dawdle along in the left lane. If someone runs up on me doing 100, I happily move over, I depend on them to get the tickets and it works well. I do not tailgate. I really try to be nice, let people in that use blinkers and such. I have two guilty pleasures. To date, no one has passed me in the right lane only to squeeze into the 6 car lengths between me and the person I am waiting on. I break my rule there, I have no issues closing up all the space. As soon as the right lane offender gets plugged up behind the 40mph Winnebago and passed by 20 cars before getting back in the left lane, I back off to my original following distance. The other guilty pleasure is finally picking your way to the front to find the guy below the speed limit who refuses to get out of the left lane. Everyone passes them on the right. I make it a point to clear them with a 20 mph differential and clear them by 1/2 length or less as I move back to the left lane. They usually get the point. Oops, one more guilty pleasure. If I am towing or driving a big truck I will put the blinker on and wait, let the people beside me clear out and such. At a certain point I just start turning the wheel. I figure the people racing up to block off the hole were warned and if they can't be courteous, neither will I. Oops, 4. Left lane closed ahead for construction? I get in line when I see the signs. I watch people whiz past. At a certain point; after many signs, everyone can see the arrows and the merge in cones, I just block. Why is their time more important than anyone elses? Another bad habit picked up from truck drivers. I can understand emergencies, saw one a while back. Flashers on, moving down the shoulder at a sane speed. Tinted windows, thump, thump music, and cut from shoulder, traffic, closed lane, shoulder again? Prolly not an emergency. Other patient drivers usually get the clue and help lay the block down. It helps to value your paint less than the other guy.
All those are calculated risks. The safest course today is just ignore the other drivers. Anything else can end in jail time, morgue time etc. I have an issue though, growing up around race cars I know there is a right way to drive and an asinine way. Cars become conduits for people's emotion. Person in control, car will be in control. Person typical me generation will drive like it. 10 years ago I'd get road rage. Now, having raced cars, I know pretty much what I can do with the car. Carrying a gun I know how it can escalate. Not worth it. I don't get mad on the road, just probably won't tolerate blatant disrespect.
Blatant disrespect defined: Same car OP describes. (Boy, that guy gets around!) I'm cruising at 75 in the right lane of a 65, no hurry, following a few other cars. Rapidly get overtaken by a string of cars. Their funny colored headlights bouncing on poorly modif.. mangled suspension communicates their demographics to me long before they reach me. 4 or 5 bumblebee by me doing 90-95, more coming. Tail end Charlie sees the winning move and proceeds to try to pass the whole string and me....On the right shoulder. At 85mph his front quarter was even with my passenger door as my right wheels touched grass. Oops for him. Suffice it to say I was a little pissed. Slowed down to about 60 and cruised, never saw him again. Maybe he launched into the pines, maybe he stopped to clean his pants. Don't really care either way. Why? One, I have been laying under a car on the shoulder fixing it numerous times. I know cops don't like shoulder drivers. I don't mind if said bad driver leave the gene pool without taking anyone else. Two, I cannot stand that level of disrespect. Not PC, not the safest course, I know.
But generally, just get on down the road and try to know what everyone is going to do before they decide to do it.