Is there a way to alter the consistency of SMB like you can do with american buttercream by adding liquid? I would like to have a thin consistency SMB, is this possible?
You control meringue buttercreams with temperature, not liquid. If you add too much liquid (like a puree or chocolate) you'll break the emulsion.
Why do you want it thin? How were you planning on using it?
When I use ABC i thin it to do a dirty ice so I wanted to do the same with SMC? How do you thin it with temperature?
You don't. How you ice a cake with SMBC is completely different then ABC. You don't thin it or thicken it. You use it as-is at room temperature.
Don't thin it with temperature lol! You can crumb coat with the normal consistency buttercream if you want. Here's a vid I just quickly found on youtube, looks the same as any method I've ever seen for it:
This means that you use the meringue buttercream for crumb coating while it is still freshly made and kinda warm.
Once the buttercream has cooled all the way down to room temperature, you can slather on a nice layer that you can smooth easily.