DIY Smoked Grains?

[angry_gopher]

One of my favourite styles is rauchbier, is there any particular wood that is better for smoking the malt grain?

 

[GRJBowers]

Brewing Classic Styles implies that beech wood is traditionally used in Germany. Oak might be a good substitute, but apparently it's a little stronger than beech.

 

[Pappers_]

Hard woods are better than soft - no pines, etc.