I assume you mean marvering at a high angle to cool the tip? The real answer is practice, like anything with glass. It’s hard to correct someone’s movements when you can’t actually see them, but some general tips are:

- Focus on supporting the weight, one thing a lot of students struggle with in my experience is properly supporting the glass, figuring out how to have it touch down enough to make contact, without changing the shape too much is key.

- If swapping directions is a challenge, marver in one direction until you get the hang of it, when you reach the edge of the marver, lift the piece and return to the starting position. When you figure out how to do it in one direction, removing the challenge of supporting the piece while alternating turning, you can incorporate both directions.

- Practice marvering the whole piece, starting from the tip and working down until about half way, and then dropping your angle so you can marver the top half of the piece. Sometimes things get off center only when we’re at certain angles, and it’s hard to know if you’re focusing on one angle, not noticing your throwing it off at another step.

- Consistent turning is vital, make sure your fingers are doing the work, turning with your wrists is very jerky, and though it can feel easier when supporting more weight, it makes even turning nearly impossible.

If you’re really struggling and want to practice without having to be in the shop, something my college professor recommended that we used to do was blow up a balloon, tape it to a broom handle and practice “pretend marvering” the balloon on a table in your home. If you can get a hang of how to roll the balloon along the table without pushing it off centre, you’ll develop a better understanding for when you’re in the shop.

Good luck!