Are you doing a basic cleansing enema before the garlic retention enema? It's really helpful to run a full bag through to clean out pockets of gas and whatever is up in there first. Plain warm water or add a little Sea Salt
The method I use I got off the internet a few years ago, it was how I learned. Like if you use a bag, or adjust wtih a bucket, whatever......
Start with a small amount on your left side to cleanse just the decending colon. Release, then insert about a quart
or so, reaching into the transverse colon on your back with hips elevated, release. Then a whole bag, turn on your left side letting it reach the ascending colon, and repeat another full bag if you feel it's not free of junk yet. You might feel or hear a gurgle as it pass through the bends.
Garlic enema's are wonderful, and retention gets them into the bloodstream and liver, but you want the colon to be clean so that you don't absorb the toxins from the colon with the garlic. Plus, getting out all the pockets of gas will enable you to retain longer.