here is what i do...
we design the sign in whatever program i am working with that day or some of the people that have worked with me in the past prefer one to another...i primarily use corel.
from there we duplicate the sign multiple times and break the design down into the various pieces that we will need for fabrications for example the backgrounds for channel letters and we delete everything else....
from there we generate g code for the backgrounds of the channel letters and route them out of dibond in most cases.
then by hand we build the cans around the dibond backers...it is not a difficult process.
then we have a file for the faces and we route those out of acrylic, flip them upside down and go through everyones favorite job of applying trim cap. Yippee
we use Neon Wizard for design patterns for the neon units and move on to that step.
the raceways are about the most straight foreward step in the whole job as it is in almost all cases just square sheet metal work. and we print out the dimensions from our design and get to work with the shear and brake and build the peices.
then wire the bad boy up, assemble all the elements, hook it up to power and throw the switch....
the software in my opinion is the least of your worries, it is earning the experience to do the job efficiently (profitably) and most importantly at safe high quality standards....next is acquiring the tools to do it, yes you can cut the pieces with a jigsaw or other method but a cnc router makes ALL the difference imho. and the bigger signs you are going to make the bigger shear you need, the bigger brakes you need, the bigger router you need, the bigger tables you need to assemble the letters, the bigger space you need for storing neon units, for the bigger space you need for building the signs....the bigger trucks you need for installing the signs, the more higher end sign guys you need to higher as you can't do all the work yourself and you dont want to employ the bottom of the barrel when you are building electrical signs..or any sign for that matter imo, the more insurance you need to have for building electrical signs, the higher standards you need to have in your shop to be UL recognized...i could keep going and going, but the least of your worries is software imo