CONSIDERING YOU'D BE USING THEM BEFORE DAYLIGHT OR CLIMBING DOWN AFTER DARK, MUCH MORE DANGEROUS. EVEN IN DAYLIGHT IT CAN BE TRICKY.
I WORK FOR THE LOCAL PHONE CO. AND IF YOU DON'T HOOK POLES REGULARLY YOU TEND TO GET RUSTY. BUT JUST LIKE SHOOTING OUR BOWS, IF YOU PRACTICE YOU CAN BECOME PROFICIENT. IF YOU THINK YOU'D LIKE TO TRY IT JUST MAKE SURE YOU GET CLIMBERS DESIGNED FOR TREE WORK. LINEMAN HOOKS HAVE SHORTER GAFFS FOR SMOOTH POLES, TREE HOOKS HAVE A LONGER GAFF TO PENETRATE THROUGH THE BARK AND INTO THE MEAT OF THE TREE.
YOU COULD PRACTICE BY JUST GOING UP A FEW FEET AND GRADUALLY GOING HIGHER AS YOU FEEL MORE COMFORTABLE.
SOMETHING ELSE TO CONSIDER IS THE NOISE MADE BY YOU DRIVING THE GAFFS INTO THE TREE.
BUT I GUESS, MOST IMPORTANTLY, REALIZE THIS IS MORE DANGEROUS THAN OTHER METHODS.

BEST OF LUCK!