They would just reduce the risk of failure, why not? Drinking something has never seemed like a reliable method to me.
Go for it. It should work, I'm just not a fan of putting poison salt up my butt should it fail. What would the consequences be to your rectum and insides if you fail that way? How much would the SN burn your skin if you jumped into a bathtub full of it? I haven't heard of others injecting SN… you could be the first trailblazer.
These routes should work, but they just carry risks that haven't been reported to the best of my knowledge. Drinking it has been successful based on numerous accounts on here. I believe enema has been successful as well, but I can't say that with absolute certainty.
In any case, I think you should research here and elsewhere before making a decision to try these different routes.