Not sure about the first post of advice you recieved, but if you're new to dairy showing I'd suggest finding a Hoard's Dairyman magazine and inside there's a advertisement page of a DVD that shows dairy grooming last time I looked. I've clipped a few, but would have a hard time explaining it on paper.
I will say that dairy animals are clipped short with everything from their front shoulders forward being very short. There head and poll are short also. The cut off line between "very short" up front and "short" for the rest there body is in the shape of a "V" beginning down at there dewlap and widening out to the shoulder up by the point of attachent.
I realize this isn't very descriptive but it's the best I can do on paper.
If it's a while before you show, depending on the condition of the animal's coat at this time, I'd slick shear the whole animal as long as you've got a couple of months for it to grow back before the show. This way, you can start out grooming new growth and if washed and squeegied (sp) daily, you'll have better coat to work with. Good luck to you!
The Holsteins my son shows are completely clipped down, whole body on everything from a year up. If she is a heifer without much depth you might want to leave a little belly hair creating the illusion of depth. You also clip their heads, ears(inside and out), and udders. Any other questions let me know. Good Luck!