I've tried that, and if your fingers don't melt or you drop it in the sink, it can be fast and easy. More so if you do it regularly (don't let it get too nasty before cleaning). Especially if you're not after 100% clean (which makes no real sense to me since it's going to foul with the next hit?).
Detergents are a big plus due to 'surfactants'. These chemicals lower the 'surface tension' that holds the trash to the glass (or the 'dirt' on your hair, shampoo is another example of this). This kills that 'oil and water don't mix' issue so the wash water not only loosens deposits, but makes them more attractive to the wash as they are made less attractive to the surface they're stuck to. Different from soaps which bond with water on one end and grease and other stuff on the other end of the molecule. Detergents, generally, aren't 'used up' in the process of floating junk away.
https://en.wikipedia.org/wiki/Surfactant
Add to that the 'Oxyclean' effect in specialized detergents like PBW and you can watch tiny streams of bubbles 'attack' deposits, get under them, and float them clear. Fun to watch. You can revive that nasty bong from your blazing days this way. Bring some over to a friend who has such a bong hidden away and watch them watch in amazement and delight.
PBW is so cool/effective it has a huge thread all it's own (half the size of this one):
http://fuckcombustion.com/threads/pbw-the-chemistry-of-clean.7854/
It also contains buffers and chelants so it works well in hard, acidic or alkaline waters. Handy to have if you need them with your tap water? FWIW, they too can be 'used up' if there's not enough present.
Clean it any way that suits you, I just suggest you try detergents. Solvents, like ISO are IMO a bad plan. They have fire risks you don't need to take, higher cost, disposal issues (you weren't going to pour it down the drain, right?) and can never get your glass 100% clean (without a LOT of rinsing) since they always have a trace amount of stuff in the final rinse that will deposit again when the solvent evaporates away.
Regards to all.
OF