I love bristenose plecs, would love to have one, but have not done it for the same reasons as GirlieGirl. Couldn't stand to see one get done over, even though I have heard good results too.
How slow is slow ? I would say hours perhaps using the drip method :
1. Fish in LFS bag & Water
2. Put fish and water in bucket. Nice large one - 14/15 litres
3. Set up aquarium line from tank with one of those nozzle sorta things that you can adjust flow with.
4. Start siphon from tank with nozzle turned to slow drip into the bucket
5. Wait and Wait. No harm to have a heater in there to keep temperature.
6. Bucket fills; remove fish, place in tank.