Well Gang,
Yep, I have to agree with the "Push on" type. The Freightliner chassis under my coach is loaded with them. Now, I will admit that about 99.9% of them are at solenoids or mounted fittings of some sort but, non used for "Splicing". But, if I had to do what the OP had to do, I'd use the push on/in type all day long. In fact, I plan on adding a short line to the shrader valve on the bottom of my coach and run it to just inside a nearby compartment.
My coach looses about 10 lbs. of air a day, while parked in it's home, next to our home. Every once in a while, I have to crawl under it and feed it some air, to bring it back up to normal height. So, I'm planning on using those push-in/on types when I construct this little addition.
Scott