I'm a bit of an enema fan, although I haven't actually done one in quite some time.
It's a much more thorough cleansing than a douche as it rinses out the colon as well as just the rectum, but it takes longer to do so it lacks the immediate convenience of a douche. However, that's part of the fun if you incorporate it into some BDSM play; it becomes part of the whole scene, and there are lots of bits of equipment you can use if you're into the whole medical fetish thing - rubber sheets for instance.
The Higginson syringe is the most basic piece of kit. It's a rubber tube with a squeezy bulb in the middle, to which you attach a rectal catheter. The other end is then placed in a basin of (preferably) warm water with a pinch of salt, and you gently squeeze the bulb to pump the water in. This method is OK if you have an assistant, but it's a bit of a faff if you're on your own and it's harder to relax into things.
A better set-up is to get a 1litre enema container, which is hung on a hook or placed on a higher surface so that gravity does the work for you. It will have a longer tube and catheter with a tap valve, and is much easier to work with if you're on your own. You can control the rate of flow and take your time over it.
The catheter needs to be inserted fairly deeply to get the water up into the colon, but it's just a question of relaxing and being gentle with it; it's not painful or difficult. Lying on your left side is usually the best position.
An enema is actually a very pleasant and relaxing experience when you take time over it - often people who have had one in hospital situations haven't liked it because it's been administered too quickly. If you feel the need to expel during the process, just stop for a bit and gently massage your abdomen until the pressure eases, then you can continue.
It's pretty easy to take a full litre of water; with a little practice you can take two or more, which gives a pleasant feeling of fullness. I like to then insert a butt plug and retain the water for as long as I can, although that's not usually very long to be honest - certainly not long enough to feel safe leaving the bathroom! You can also get balloon catheters that can be inflated to remain in place.
Some oral or manual stimulation at this time can be surprisingly horny.
When you do expel the water, there is a strong emotional release as well - you really feel like a lot of psychological and emotional baggage has been flushed out as well. I think that's probably the main reason I like enemas; I always feel calmer and very relaxed afterwards, which is a good state to be in if you're planning a follow-up session of anal sex.
It's probably wise to wait for 30 minutes or so afterwards to make sure you've expelled all the water. Quite often I've found the need for a second visit to the loo, and you don't want to be in the throes of passion if that happens!