A walk-in would be awesome, but a considerable investment in money and maintenance. I used to work in the restaurant biz and know first hand; they are a pain.
The main purpose of aging is to reverse rigor mortis, so aging is important. When the weather is cool (40 degrees or cooler) I hang the deer in my garage for approximately 48 hours and then I process it as normal. However, if the weather is hot, like right now I'll quarter the deer, wrap the meat in plastic wrap(sometimes ice can cause "burns" this will help prevent it) and pour ice over the meat. Allow to sit for an hour, then pour off excess water and add more ice(this step helps to get the meat cool as fast as possible. Within 4 hours of killing the deer, you want to get the internal temperature of the meat cooler than 40 degrees to help slow bacterial growth). I allow it to sit in the cooler for 48 hours checking it twice a day, pouring off excess water and adding ice.
Btw, this step is not neccessary with the loin(back straps) or the tenderloins (filets), these muscles are already tender enough, but if you like, you can process them as the quarters above.