When it comes to making icing bows there are no magic tricks. You just need a bit of patience while you wait for the gum paste or gum arabic in your icing to set. Just pack the holes with tissue paper while they dry. Tylose is a lighter color than the gum arabic so you may prefer that.
If you want to buy a cake with the bow design my friend Karen Hill at Wedding Cake Art Sydney makes these to order. http://weddingcakeart.com.au/ She also runs cake decorating classes.
