Send effects in Reason come a long way. In this video tutorial about Reason I will be talking about using Send effects the right way! I will be presenting two different methods on how I normally apply sends. One while using a combinator as a send effect unit (which turns in to an audio effect unit to process that audio). This could eventually lead to its own unique send effect bus if you want. The sky is the limit (or in this case your CPU).
The second approach is a more daring one. Since once you start understanding the idea what a send effect bus is (eg: a parallel effect where multiple signals are joined together in an output bus) you can re-arrange the SSL mixer doing just that. Once you have experienced that approach you realize you have unlimited sends to your disposal. Thus never have to use the default sends ever again. I might note, it requires a different way of thinking (since you have to look at the SSL mixer different). In case things get too complicated, you may forget the idea about this one too ;) No worries
I hope these ideas are helpfull!
Have fun with using send effects in Propellerhead Reason!