Whittle balsa wood strips, cut up toothpick tips, or shave thin plasticard rods into small pikes of about 1/2" in length. With a pin vice and hobby knife, drill out a few holes in the tusks to plug your spikes into. It's very important to plan where these spikes will be pointing ahead of time! Think about it and test fit as you work. Always be careful when using modelling knives, as they are very sharp.

Secure your spikes in place with a tiny drop of super glue. In addition to drilling holes for spikes, lay a few down flat and point them towards the front of the model so they're in line with the tusks (as shown in the photo on the far right).

Next, get some 32-gauge, cloth-wrapped wire. This stuff is available at any floral shop or craft store. It's a bit easier to use compared to plain old string, as it holds its shape and can be bent and twisted as you see fit. Wrap this wire around the tusk and spikes as you please. Just go slow and try crisscrossing the wire as you go. There may be points where you'll have to cut the wire and start a new wrap going, but these stops and starts will add to the overall feel. Lastly, add a single wrap of wire further up the tusk to complete the project.