Hi Warren,
I feel that in 1/72 you want to have the impression of wood without over done grain, but enough there to make it look like wood. You also want to go for a little bit of variation between panels as well. It's a fine thing and really up to the individual about what they like to see.
I use a method similar to François' method, using oil paints (various mixes of burnt sienna, raw umber, yellow ochre, black and white). Agree that you should let some of the natural oils leech from the paint first. Apply with a medium sized and slightly stiffer brush; too soft and you'll lose the effect. Don't be afraid to have the brush slightly moist with thinner as this will help create the grain effect. "Jiggle" the brush about to get a bit of a 'wobble' in the grain, if that's an effect that you like. In my personal opinion, too many straight lines looks unnatural (even if it might be more technically accurate). You can dab on tiny dots of darker paint and 'draw' these across the panels to help represent knots or variations in the ply, to your taste.
For example, here's what I went for on my 1/72 Airfix Albatros D.V. After the oils are on, it looked like this:


I did this all in one sitting, working each panel from the forward fuselage back to the rear. You can see the effect is quite exaggerated, both in terms of the grain, and panel variation, but this is quite deliberate.
Next, once the oils have COMPLETELY dried, comes a clear yellow coat. This helps to 'tie' the panels together visually a little more. It reduces the effect of the grain as well as reduces the differences across each panel, whilst still providing the variation you're looking for.


I also used to use thinned clear smoke around the edges of each of the panels; this creates an interesting effect but is easily over done. I have steered away from this in recent builds (including the Airfix build herein) but it can also produce some interesting effects.
Once this dries, apply the rest of your markings, and decals. I then use a raw umber wash to highlight the panels. The wash is the final step in drawing the whole effect together. Here's what it looks like:



Some may think that this is over done, some may think it's under done, too yellow, not yellow enough, etc... it really is a personal choice. Ultimately you are the one that needs to be happy with it

Practicing on cheaper kits will help you to figure out how to get the effect you are after.
Hope this helps?
Cheers!
BC