make a copy of the crest as it's going to be, alongwith 3d transformations and everything. decrease brightness/contrast to -100 (both and twice if required) to obtaina black silhouette of the crest. motion blur this silhouette. set the angle to whichever angle you want the extrusion to be in and the pixels to the thickness. merge this blurred layer with a white layer. use levels to convert even the lightest greys to black, leaving only the purest white as white. remove the white using either the magic wand or Mac's Remove White filter (available at http://deepspaceweb.com). use hue/sturation to colorize this to whatever colour is required. Add another motion blurred layer above this for an interesting 3d effect (obviously do this in a colour that stands out). align the three layers to obtain the extruded crest (the layer with the original crest, the one with the extrusion and the one with the motion blurred crest in a contrasting colour). that should do it! lemme know if u face any probs/difficulties or if there is any other query!