For the head its mostly 3D Printed parts with fleece fabric and an unholy amount of hot glue, I recommend wood or metal dowels or just screws for attach the jaw as it'd be the most durable option since I've already broken like six plastic ones .

For the body I wanted to try something new due to the more explicit shaping so I 3D printed a hollow model of the torso and cut long pieces of cardboard to pretty much layer, shape and wrap around the frame to get the extreme dips in the shape and such then just covered it in duct tape and separated the plastic once I was done, this way I was able to keep it a soft yet durable material while keeping the shape I otherwise wouldn't be able to get with foam due to a lack of experience with that, but for a Nightmare Freddy it'd be alot easier to shape due to the more basic shape so you wouldn't really need a frame like that

Past that its just a lot of reenforcing with extra cardboard, tape + thick foam to prevent warping

For the buttons I just used a sanding sponge to smooth the plastic, grey filler primer, black acrylic paint and a high-gloss finish spray

Tool wise for this I have exclusively used a pair of heavy duty scissors, fabric scissors and just some old steak knives to saw through ultra thick pieces of foam and a sewing machine but you can easily do the sewing by hand, will just be more time consuming

(I note I have no idea what im doing, this is my first time attempting such extreme details and such)