The model I'm building is a Soviet IS-3M Stalin from Trumpeter. It will be airbrushed Russian Green (Model Master enamel).

I don't want to weather it with dirt but I would love to achieve the kinds of highlights and shadows as seen in these Academy Tiger kit photos. How to do this?

I think have a good idea on how to make the tracks look nice. I will be using individual links from Friul and airbrush them buffing Burnt Metal...after buffing with a piece of cotton the raised detail on those should receive a nice highlights. However, I'm not sure how to treat the tank body.

One of the ways to achieve those highlights are to wash and drybrush. The wash makes the recesses like panel lines have a darker color and the drybrushing gives the raised detail a lighter color. This way you have 3 shades (dark in recesses, regular in flat areas, and lighter in raised areas).

I don't want to weather it with dirt but I would love to achieve the kinds of highlights and shadows as seen in these Academy Tiger kit photos. How to do this?

The only way to get the look of the Academy photo is by wash and drybrushing. A wash is basically thinned paint (burnt umber) that is used to darken the shadows. Dry brushing is just that, going over the model with a brush with a trace of paint on it. The impact is too bring up the highlights of the vehicle. There is a great article on weathering to be found on this site. Take a look at it. It will help.

Monster,
Check out the article on weathering that GSP mentioned. ( Weathering Heresies by Paul Owen ) It's a good one. This may stir up the hive but I think the drybrushing on the Academy Tiger is a bit over done, like they wanted the model to look like an artists painting.
No offense to other opinions out there. The two cents there on the table are mine.
Good Luck

Highlights on black paint can be done with graphite from a pencil which has been "SHAVED" onto a palette then a small amount placed onto the brush and "painted" onto the surface.
I have an article coming out about this soon...hopefully....Jim_staff.
You can wash and dry-brush all you like...but practice makes perfect.
To dry-brush, add a little white to the base colour and clean off the excess untill the brush is almost dry to the touch.
Then pass the brush over the raised areas to achieve the high-light..
As I say, there is no substitute for practice, so try on a peice of scrap first.