RULES to perfect signature making.
#1 Don't use enormous sizes.
#2 Learn about brushes, c4d's, lighting and flow.
#3 Don't say anything is good unless you know you put effort in.
So yeah my CnC for you would be to first of all make them smaller, preferably around 350x100 / 400x150.
The next thing you need to work on is rule #2, search for tutorials to help you if need be.
Then last but not least, make sure you perfect it with a little sharpening here and there, but not too much.