Well, first of all, don't use hot water - it causes flash rust. Cold or at the most lukewarm water is all you need. And you don't need 'soap'.
Second, like Hawg said, dump the petroleum based oil. Use an oil meant for black powder guns like Ballistol.
Plain, cold or lukewarm water works. Thousands of shooters use it every day. If it didn't work for you, you're doing something wrong, like shooting the gun with petroleum based oil in the bore, and using very hot water to try to clean out the burned oil residue.