First of all, a few terminologies and clarifications which I think you may have some misunderstanding. When you put midi sequences into wave, it is not called bouncing. Secondly, midi sequences are basically midi information - they contain messages like which notes are being played (C, D, E etc), the velocity of the note (0-127), the duration of the note, any controllers being used for the note (cc#) etc. They contain no sound. So there's no way you can add any effects/reverbs to them.
To generate sounds, you need the midi sequences to trigger a sound generator which can be an external sound module, an external keyboard or a VST instrument (VSTi - which can be a softsynth, a softsampler etc). After THESE sounds are recorded (ie into wave files within your audio software), you can then add reverbs/effects with VST effect plug-ins to them. That's the ONLY way to do it, which is what I said previously (and what your friend is trying to say as well). You cannot add these reverb or effects to midi sequences as they are just signals and messages.
Bouncing works only on audio tracks. It refers to combining a few audio tracks into one. Sometimes, we run into the problem of having too many audio tracks - either too many for our PC's CPU to take, or too many for our hardware multitrack. We then bounce a few tracks into one track and therefore effectively decreasing the number of tracks, and freeling up more tracks for recording.