Just cut the top third off the thorns, otherwise they can shrink back quite a long way into the wood and are sometimes the way in for fungal and other infestations during the seasoning............and cover all the cuts you make with wax or even oil paint to stop 'em drying out too quick.............
If you only have one or two sticks to bend you can soak a towel, wrap it around the stick and cover with tin foil (shiny side in), then hit it with a heat gun for a good while 'till the steam from the wet towel gets into the wood; then bend to your will!
You can make a jig for the handle shape you want by drilling holes to fit 18mm or bigger dowel, drill into a piece of scrap ply either side of a drawn outline of the shape you want, steam the stick and bend/manouvre it into the channel you've created with the dowels............another thing that works well is to fix a pulley wheel of suitable size onto a flat surface, and bend your handle around that to the desired shape. A decent selection of clamps will be your friend, but it's amazing what you can achieve with wet cotton string, it tightens as it dries and so holds things in place very well.
There are almost no circumstances with sticks where "this will work; this will not", you have to mess around and learn as you go, it's as much to do with having a feeling for the stick in your hand as it is to do with hard-and-fast rules. But it's a huge amount of fun and satisfaction trying and you won't be long about finding some little trick to post here that nobody else has thought of.