Is there a tool that is able to transform a multi-band image to single band rasters? I usually use the raster calculator within the modeler to do that.
You could use
gdal_translate from the new workflow, which is under:
Raster > Conversion > Rearrange bands...
You won't be able to select the pencil as in the past, but you can select only the band you need from the UI. You also get the python code in case you want to use it in pyqgis:
gdal_translate "path/to/raster.tif" -b 1 "path/to/result.tif"
To get band 2, replace
-b 1 with
-b 2 etc.
Note: you may need to enable the GdalTools plugin.