The gravel should help if it's from a well established tank pad will make all the differenceI could probably cut the pad in half and put it in my new tank I also put a Scoop of gravel in a mesh bag and a rock from the tank in there but it's just not going fast enough
Anything from the established tank will speed up the cycle, used media is the best, however substrate can help also, as you have suggested, if you are doing a fishless cycle increase temp to 30'c and add as much surface agitation as possible, air stones etc, spray bar positioned about waterline.
This should all help towards getting the bacteria to establish itself quickly.