If you want to hem the body, do that now. Turn up the bottom, iron and sew. I quite like sewing a false band with my overlocker. I turn the hem back on itself and then sew around the fold.
If you don’t have an overlocker, don’t forget to finish the edges with an overlocking stitch or zig zag, and use a stretch stitch.
We’re going to make the hood now.
Lay a hood that fits, on top of your sweater, going with the grain (up and down the sweater). You’ll do this twice, once for the outside of the hood and once for the lining. These could be the same or different, I’ve done one of each (the sleeves of one of your sweaters, cut open and ironed flat might be a good size for the hood pieces. Don’t forget you need two layers).
Cut out the hood, lifting it up to cut a straight bottom edge. Then, cut a strip off the front of all your hood pieces, leaving about 5cm (2″) at the bottom. Curve the bottom of the cut-out.
You should have four pieces cut out for your hood. They might be all the same colour (like the grey/pink hoodie) or two of each, in contrasting colours (like the red hoodie).
Pin and sew your hood pieces, right sides together, along the back curve and up the front at the bottom. Turn one hood inside out and the other the right way out.
If you don’t want fluff in the hood, leave the next step out.
Fold the fluff for the hood end to end, right sides together, pin and sew. Next, fold the fluff in half lengthwise, wrong sides together. Ease the fluff, raw edges together, evenly around the face opening of the right-side-out hood. Raw edges together! (photos below!)
(non-fluff people come back! You need to do the next step, just ignore the fluff)
Carefully slide the wrong-side-out hood over the top of the other, so that the face openings match. Pin together the hood-fluff-hood sandwich. Sew. Phew!!!
Turn the hood the right way round, through the neck hole. Wow!!! Look at that great fluffy edged hood!!!