I have used a small file on wire cutters and it worked pretty well. As for scissors I just cut fine sandpaper. I never had to do that with my fiskars scissors though, but some of my older shears that I use on leather needed it a few times. With scissors you need to make sure that they are still touching as you close them. Some of them get loose and can spread apart, which will make them not cut and make it seem like they are dull especially with older ones.
Some cutting edges are very hard and a softer file will not touch them. A small diamond sharpening stone will work. Each type of tool has its own cutting/shearing action design. If the tool worked when new, then try not to change the angle of the cutting edge.
If you are looking for a simple solution
Just get the inexpensive pull-through carbide sharpeners for scissors/one sided blades
Cheap and effective and super easy to use
Perfect for inexpensive tools/blades that are sharp on one side
They work great for inexpensive cutting-edges
You just need to get the right type
There are two types, one for one sided scissors/cutters/blades and another for two sided blades
They remove a lot of material, but my $.99 cent paring knife and scissors that I use every day get real sharp, real fast.
They don't do serrated edges
Yes, they do remove more metal, but it is nothing compare to the speed and efficiency on cheap stuff
I have a Ken Onion Work Sharp, but I am not going to make it a science project for cheap inexpensive knives, scissors, machetes, whatever from china/insert cheap exporter country of origin. The dollar blade get the three dollar sharpener.