How does one hone their skills for a one time event shooting a wedding as a gift to the person because there are no funds for a wedding photographer? I also wouldn't want to assume that skills need to be honed. If one needs to gain 1.5 to 2 stops better ISO performance, contrast, metering, etc with wider views as one might want for a wedding for this one situation, then a better camera fits the bill IMO.
If the skills of the person is constant, as is the scene at hand, then fast lenses and/or a better body will make for better results. A rental won't cost much and assuming that skills aren't going to magically improve dramatically in two weeks, a better tool will make for better results. If the wedding was 6 months out, then yes, I could see going out and trying one's hand at shooting such an event in low light, poor light, or tight quarters being beneficial. It provides time to learn lighting, post processing, and different lenses for different effects, but alas, there are only 2 weeks with 2 major holidays in the mix right before the wedding.
For many people weddings are not something you attend to that often. That said trying to predict which situations you might find yourself in and what is challenging e.g light, focussing, standpoint and angles of view where the wedding takes place. Train Changing lenses if deemed necesary, find the optimal settings and how to change them if necesary, where when and how to use flash. In other words prepare yourself for the upcomming event instead og staring blind on gear that light come in handy if..... That wont do you s..t if youre not prepared and not certain what to do.