GarageSale is good for hobbyists too, because it's worth it to spend some time developing a decent template. Your listing will just look much much better, you can have the images down with the description, etc. It's also good because you can schedule things to post at a certain time without paying eBay $0.10 per listing.
On the mannequin, you'll never have one that fits everything. Learn to pin them. I use chip bag clips on the back to hold the excess material and it works up to 50L pretty well.