I’m 5’ 5" (and a relatively wimpy 67 year old woman) and have solo loaded kayaks and canoes up to 80 pounds on all heights of vehicles. It is true that the longer the boat, the easier to load, even if longer boats are heavier. Method depends on weight of the boat – with most 14 footers being plus or minus 50 pounds there are a few options.
Having a spoiler does not necessarily mean you can’t load from the rear – my Mazda wagon has a spoiler and I just throw a rubber-backed bath rug over it so it doesn’t get scratched and shove the boat over it. If you don’t want to do that you can carry the boat with your shoulder in the cockpit to the car, stand beside it with the boat closest to the car door, facing the hood and angle the bow up into the front j-rack, then lift the boat slowly while walking yourself backwards towards the stern and lift it into the rear j-rack. There are also devices like the Roller Loader that put a set of wheels above the spoiler that you can rest the bow of the boat on and then shove it forward onto the racks. Depending on the height and placement of the spoiler, even one of the suction cup base shower grab bars can be placed on the vehicle to provide a sliding platform.
I also carry a small 2-step folding household step stool. This can be a help in getting the boat up to a comfortable pivot height and also for getting up to roof level to fastnen down the straps. Speaking of straps, put them over the racks BEFORE loading the boat. I use 9-foot and 12-foot 1" NRS and Thule buckle straps (never use ratchet straps on a kayak!). Loop one around the middle of each rack, the 12’ in the front and the 9’ in the rear, and drape the ends over the hood and tailgate so you can reach them once the boat is on the car. Once the boat is on the rack, it’s easy to grab the ends and toss them over the kayak towards the outside of the car. Then pull the free end until the buckle is at eye level about halfway up the side of the boat, wrap the free end around the near side of the rack (and also around the car factory rack if it has a lateral rack that the Thule bars are attached to), connect and snug up the buckle and tie off the ends with a few more loops around the bar so it won’t flap in the wind. Then ALWAYS tie off the bow and stern with rope or straps to the bumpers of the car. If you can’t find a tie off in the front, you can get loops of nylon strap attached to a short bit of rubber tube that you trap under the car hood to tie off to.
Honestly, one way I load, without j-racks, is to lean the kayak upside down against a wall or railing and get under it with my head inside the cockpit and carry it on my head, balanced and grasping the cockpit rim (coaming) with my hands. This puts it high enough that it is not that hard to lift the bow slightly to rest at an angle on the roof rack, then lift it enough to get my head out of the cockpit and walk my hands back to support and lift the stern end and slide that onto the rear rack. I realize this sounds whack, but it really is easier to carry heavy loads directly over your center of gravity, as you can see looking at people in third world countries carrying enormous burdens on their heads. The seat padding in most kayaks makes them not uncomfortable on your head.
Boats seem dauntingly heavy when you first try to handle them. but once you get the feel for the weight and learn how to use what strength you have and, more important, how to balance that weight, they become not that difficult to load.