Well, I was trying hard, but my 13 years old brain can't handle cone tracing.
Do you know any other, easy to implement, real time global illumination techniques?
The words easy and global illumination don't really get along all too well
Indirect lighting is an advanced technique, so if you want to implement it you'll pretty much have to get your hands dirty
When it comes to global illumination you have quite a few options each with their own advantages and disadvantages.
There are precomputed methods like precomputed radiance transfer (PRT), photon mapping, lightmap baking, etc. These techniques are mostly static and won't have any effect on dynamic objects in your scene, but they are very cheap to run since all the expensive calculations have been done in a pre-processing step. These only support diffuse indirect light bounces as far as I know.
When you look at more dynamic approaches you have VPL-based approaches like instant radiosity, which allow for dynamic objects and a single low-frequency light bounce. You could also directly use VPLs, but this will require some filtering algorithm if you want to get smooth results and prevent flickering.
Another interesting dynamic approach is the light propagation volume approach used by Crytek which uses reflective shadow maps to set up a 3D grid with indirect lighting values, and which then applies a propagation algorithm to correctly fill the grid. This is fast, but also only allows for a single low-frequency diffuse bounce.
There's also screen-space indirect lighting, which is an extension of SSAO. Of course this technique can only use the information available on screen and could possibly not give satisfying results.