Hand-routing PCBs for SMD
Let me start with your last question, I would highly recommend NOT soldering components on both sides unless you have a really good reason to. I have made a few boards with double sided soldering and it became more of a pain then anything.

As for the routing itself, my answer here might help you out some, but I will elaborate some for your specific circumstances.

Part density can become an issue when you are hand soldering, but it is difficult to give exact numbers as everyone will be different with how comfortable they will be soldering and what parts it is. As a minimum you will probably need 2 soldering iron tips width apart. This will give you the room to get the iron in to work on one part while not hitting the other. You might also want to take into account the angle that you like holding your soldering iron at as you won't want to be resting your iron on another IC. If you have a shakier hand then you might want to see how much your hand shakes and space your parts at least as far as the tip of the iron moves as you are shaking.

I would also avoid running traces between legs of SMD components. A lot of people will do it just because it passes DRC, but if you are hand soldering with no soldermask, it becomes very easy to accidentally bridge to the trace.

It is also helpful, but not required, to bring your traces out straight from any ICs and then after a little room branch them to the direction they need to go. This will help you line up your IC properly as well as to be able to get the solder in place easily.

And finally, going from through hole to SMD, you will find that many of the tricks that you can use with through hole just wont work with SMD. Things like having no vias because you are using a through whole component to jump to the back side, instead you might have to go back to your schematic and change things around to limit the number of vias used. Also you can usually run traces under through hole items, but this may complicate things more with surface mount.

Overall, just practice and you will pick up tricks just like I am sure you have picked up tricks with through hole.