Main thing on a scraper is the blade mounting it at a 90 degree angle onto a stick or horn.If it's membrane than it's on the flesh side.
Here's a flesher [wider one] that I use mounted onto elk horn.Be sure to round the corners on the blade.
The blade is a piece of a cracked farming disk blade which I cut out from a disk blade with a torch.I did heat it red and dunk into some 10 weight oil to harden it farther after beveling it [about a 30 degree angle].A fleshing blade can be a little wider than a dehairing blade,but still very sharp.I only have one for fleshing.You can put a great amount of pressure on a framed in hide while fleshing to get every bit of membrane off.
The other is mounted onto elk horn too and it's blade is a chunk of mill basterd file.No reheating done on that.It's hard enough the way it is.These will hold an edge completely through doing a normal deer hide.
For a good edge for dehairing I sharpen mine with a stone.It does'nt take very long to get a good sharp edge.
Taking around 1/4" wide strip off at a time for dehairing is about the right width.Trying to take too wide of a strip will not work very well.
I keep various different width scrapers for different jobs on areas on a hide while removing the epidermis.
Hedge with the sapwood removed.
This one is only 1/2" wide for delicate areas of the flank on deer.
Rawhide lace sized with TB 3 onto a piece of hedge.
Mounted onto a pine dowel.
The best type of deer rawhide to use for backing a bow is these yearling deer or goat hides,or maybe the belly of a buck should work ok.