A couple of earlier posts mentioned to use the normal channel of the AC30. That helps a lot. Also, don't have the treble on the amp too high, around 3 or 4. Get your treble with the booster cranked. Volume on the amp is cranked, of course ( I didn't have to tell you that.) If you have a Strat, try it in the notch positions with the guitar tone knob rolled back a bit. I have found that if the tone cap in my quitar is more like .01 mfd, I can get that hollow/woody sound with the tone engaged. I have not used a Vox amp for a wihile, but that worked for me.
If you want to use a scratchy pick but don't want to heft a quarter or half-dollar (if you can find one) those Hercos picks with the serated gripping surface work well if you turn them over.
All that said, what with this being the present and all, it would probably be easier to us a Tube Screamer or Boss OD to boost the AC 30 and shape the tone, without it getting too screachy. I bet Brian would have used one if thay had been available. I seem to recall that he said his booster was modified.