Here's the exact setup of mine with part numbers...
What plastic end are you referring to? Are you talking about the plastic tips on the end of the racking cane? If so, no, I don't use that. I pretty much throw them away when I get a new racking cane. But, basically, during active fermentation, I use the center port of the cap (has the white cap on it in that picture) to run a tube to a blowoff vessel. If I feel like it, I'll replace it with an airlock after the initial vigorous fermentation. But when I am ready to transfer over, I just pull out the blowoff tube (or airlock), and slide the racking cane down through that port and go from there. Does that make sense?
Also, I put my receiving keg on a scale so I can fill by weight. This is much more accurate at letting me know exactly how much I get in the serving keg. When I first start the transfer, I have the racking cane about halfway down into the keg and I just let it go. When I start to see air bubbles in the line, I'll slowly slide it down some more. As one more piece of insurance, I added a worm clamp on the racking cane that stops it from sliding down anymore when it's about 1" above the bottom of the keg. This helps keep trub and crap out the transfer and the receiving keg.