I find baking soda enemas to be very relaxing. Nice to just lie there with a slow flow, no rush, and gently fill up with 2 or 3 quarts. I generally use 2 teaspoons of soda per quart, but sometimes a bit more. Sometimes it doesn't all come out, but that might be because I didn't add any salt, and I held it for a long time. It then eventually comes out the front side.
For a real kick, supersize your baking soda enema. After you have held the soda, then prepare a small enema with a cup of lemon juice, and probably a cup or two of water. You get in position and hang the enema as high as you can. Open the clamp and let it rip. There might be a little burn as the lemon hits, but that isn't all. When the lemon juice hits the soda there will be a pretty good reaction as the basic soda tries to neutralize the acidic lemon. The result is gas! Lots of gas!! I normally only do this with 2 quarts of soda, so there will be some room left for the gas. If there isn't, guess where stuff is going to end up?
This enema has been described many times as the "fire extinguisher". That's because they used to make water filled fire bottles that somehow mixed an acid and soda when you turned them over. In some cases, that's what might happen to you! :-\ You might want to try the first one very near the toilet or tub, just in case you can't handle it. I typically am in bed, with something waterproof under me, cock in right hand, and then open the clamp. I try for a front side explosion just about the climax of the impending back side explosion. I have only had one "accident" with this, but the potential is there. Take precautions.
As for safety, you won't blow up on the inside, as the rear end safety valve will pop first. And, yes, naysayers, please had a go at this one -- I'm sure you will find everything to be wrong and unsafe. But, I say don't knock it until you have tried it. 😮