DO NOT shower with warm water afterwards. It dampens the positive effects. Spend some time outside, a minute or so, before and hang out a bit outside afterwards if possible. No need to rush back in the house. Throwing a little cold water on your face, arms and legs is a good way to start.
Relaxation makes it possible.
A bucket with a lipped spout makes it much easier to direct the water where you want it. Filling the tap outside also gives you more time outside. In the winter when this is not possible, fill several buckets before hand. This saves the trips back in and allows you to focus more on the experience. The colder the water, the better it feels.