I had 2 nocturnal emissions (without dream) back2back despite my cold shower efforts. I'm blessed with uncircumcised willy, so as soon as I was about to release, I would wake up and ejaculate inside my "foreskin" and dump the load in the toilet later. Granted it only works if you've ejaculated before or you cum meagerly. The first load after a period of time of orgasm abstinence will generally not fit and is bound to ruin your boxers. I almost always catch it inside my foreskin if the following wet dream is less than 2 days apart from first. I'm so proficient at this now that I've begun to call myself a "cum trapper".
Just an update, I've perfected my method over the time, Now i can catch "Full blown" loads too. I'm officialy Master Cum-oshi now! The Cum TRAPPING BEAST!