This is what i use for most of my carving/detailing (made from a jigsawblade):
As long as ur knife is razor sharp, any knife is good enough, exacto, snap blades etc. Special micro carving knife set are nice to have to make easy work of doing v grooves, gouging etc but not necessary. My advice is stick to normal type lures first until u've mastered the intricacies of making a well made functional lure. Details have their place in altering a lure's behaviour but until u've mastered the basic type, it's not an area where u can just jump in & expect good results. When the details are not functional, it's just an embellishment which can be achieved with photo-finish & other painting tecniques or simple detailing which can be done with a just a file (example: the gill contour of a Rapala ShadRap). Just my 2 cents.