When I think of consistency I think of spin so you can hit it higher over the net and still bring it down. Most people I see tend to hit the 2HB flatter than their forehand. So, maybe try and hit it with more spin to create more margin for error.
I think everyone's needs involving technique may vary from one person to the next. I've recently switched from a one-hander to two-hander about 2 months ago. Since I was mostly in a transitional stage, the biggest issues for me were 1) finding the right distance to make clean contact with the ball and 2) getting into the right position with my feet. After two months I'm starting to get the hang of hitting the 2-hander. Now its more an issue of getting enough topspin to to shape the ball flight more, its especially a big deal for the balls at waist and thigh height. For some reason my chest-shoulder high backhand is more consistent, probably because I automatically already have height in the shot, whereas lower backhands need more action on the ball to achieve higher net clearance. I find the best thing to keep in mind to have a consistent backhand is to hit it high over the net and take the racquet back early.
Here are a few things I think are helpful to a good 2hbh:
(1) good preparation - I prepare to the height of the expected contact point with the ball and then I drop the head (only slightly) to swing in a mostly straight upward diagonal line up and through the ball. Don't prepare too high then hit a big loopy C or your timing will be tough and you will tend to not get under the ball (the loop only drops to the height of the ball).
(2) loose wrists - power from the 2hbh comes from the hip/torso rotation and not from swinging hard in the arms, so use soft wrists to point the racquet head down and back before starting the forward swing to get the hips to engage. To encourage soft wrists/hands, I like to play while gripping with only one finger and thumb on the forehand side hand (right for most). I like to feel my hips open before I swing with the hands
3) good extension- I like to think of the racquet head as moving in a straight line through contact with the ball. This gives you some margin for error in case you are a little early/late with the contact (racquet face still pointing in the desired direction). If you swing is too round (when viewed from above), you won't have any margin for error because early/late contact will cause you to spray balls side to side. For good extension, do not finish over the shoulder until you have fully swung straight through the ball (BH elbow is straight before taking the racquet over the shoulder)
If you are actually trying to build a BH from scratch and not trolling, the absolute worst thing you can do is ask that question here. Like 4 out of a 150 posters have clue one. And that's not even an answerable question. Do. Some. Research. Feel tennis, Salzenstein, Wegner's books, FYB. Hour after hour on a wall or a ball machine.
Just following grip or back swing or whatever isn’t going to do jack without constant practice and reps. Improvement is about reps. If you’re still asking about grip and not providing much context like a vid, you’re probably just looking to run without even learning to walk first.
A quick vid on yt and then long hours of practice does wonders. If you’re willing to put in the effort.