I've wasted many many hours with my little how to book, scraping and tweaking reeds, totally in vain never managed to adjust a reed successfully ....now I just chuck the ones that don't work and keep the ones that blow well out of the box
As a boatbuilder I've spent much of my life attacking everything from trees still standing in the forest to tiny slivers and matchstick sized bits of wood - so I've got a considerable headstart on this (even though reeds aren't made of wood, botanically speaking...)
What I use is 400 grit wet and dry sandpaper - used wet.
I first soak the reed for a few minutes in blood temperature water and test blow it on the instrument.
If the reed is too hard, remove from mouthpiece and place it, flat side down (natch!) on a
flat surface (a small beech breadboard is good - mine's teak, from a scrap left over from a boat yonks ago... posh stuff, eh?)
Wood is a good surface - when wet it has enough 'stiction' so the reed doesn't slide around. If it is a new breadboard and varnished (why?) and there isn't enough 'stiction' take the gloss off with said wet and dry (used wet!).
A small board (2" X 1" by, say, 6") could even go in your sax case with a bit of wet and dry in case of emergencies. You could wet the sandpaper with beer if need be. Take two little boards and you could help out the rhythm section on Latin numbers...
Cut a small oblong bit of wet and dry from the sheet, wet it, and using two fingers and moderate pressure, rub in deliberate strokes steadily from the top of the ramp towards the tip, stopping about half way towards the tip.
Don't use the sandpaper dry - wet works far better for various reasons.
If you look closely at reeds you will see that the ramp is slightly rounded in section. In using two fingers to apply pressure the deformation of the pads of your fingertips will tend to remove material evenly across the curve of the cross section. A knife will not remove material evenly across the curve - unless it is ground to a concave profile, perhaps....even so the curve seems to decrease towards the tip...
If the reed is so hard I can barely get a sound out of it I give it twenty strokes before rinsing and trying on instrument. Then it might need another ten strokes before another try. Keep a tally of how many strokes - you are building experience which will enable you to estimate the probable amount of adjustment future reeds may need.
If the reed is less hard then obviously fewer strokes will be needed - ten or five or even just a couple if the reed is nearly right. Better to take too little off, and take more off later, for obvious reasons...
Don't sand the tip at all unless you really feel that it might benefit from one or two very, very light strokes after having done your work higher up the ramp. Sanding the tip is a very delicate operation and best avoided if at all possible.
A very few minutes - and I mean that, it took far, far longer to word this nicely and clearly and key it in than it would to sort out a reed - will get your reed close to perfection. Five minutes, including repeated testing? Ten minutes? No more.
Don't actually try for immediate perfection otherwise the reed will become too soft as it blows in. Leave it a little hard and use for a few minutes at each practice session and give it a chance to blow in. When it plays perfectly you can gig with it. If it remains stubbornly a little too hard for too long, give it a tiny bit more of the treatment.
I believe in KISS - Keep It Simple, Stupid.
This method could hardly be simpler and easy to get the hang of and it WORKS. No more reeds rejected because they are too hard to play... and no need to ever use reeds which are OK but are not really perfect.
If you have reeds which you were going to ditch anyway because they were too hard then all you are investing is a few minutes of your time.
Reading the articles on the link will give you a lot of information on how reeds work which may not be realised even after years of playing - so it does no harm to read them. If nothing else, it shows that experts don't always agree 100%... and I bet none of them have ever shaped up a 30ft oak keel with just an adze and a plane...
Try the method I describe here. Light will dawn.
Remember KISS.