I am of the opinion adv nitrox/deco procedure certifications is the best route to go for overall knowledge and experience. It certainly encompasses all aspects of the solo cert and beyond...
It does - many TDI instructors issue a solo card at the end of AN&DP. But not everyone wants the hassle of learning about decompression.
Another good alternative is the TDI Intro to Tech course, which has a lot of flexibility in it.