I've enjoyed watching black treacle mess and decided to try it out myself.

I start wearing wet look boxer shorts and pour the tin of black treacle down my chest and it runs down my body to the top of my boxer shorts, I then pull down my shorts to expose my cock and cover it in treacle and rub it in

Then I pour a tub of chocolate custard over myself and mix it all in, my boxer shorts don't last much longer as I remove them and add more treacle and chocolate custard and normal custard until I'm covered in mess.