I tried printing the Curiosity Rover model, but slicing even one part takes ages (3h+) on my slow PC that I use to control my 3d printer with. (I’m using Repetier Host and Slic3r).
Does anyone know of a method to remotely slice files? So for example that I could slice it on my main PC and send it to the other PC with the printer then?
Would OctoPrint work for me maybe?
Thanks for any help 
Octoprint would work. Or just set up network sharing, use an sd card, use a USB, or upload to cloud based storage service. I mean all you’re basically asking is how to transfer a gcode file.
The slicer (in your case Slic3r) and the host (in your case Repetier Host) are two different programs that can without any issues operate completely separately from each other. Just install your preferred slicer on your fast machine, slice on that, save the resulting GCODE file and have the host print it.
By default, the gcode is saved to a temporary file that Repetier Host can fetch. Not positive where that is, but you should also be able to save the gcode to a text file that you can transfer to your computer and load from Repetier Host. Just install the latest version of Slic3r on a more powerful computer, then download and slice the model files (*.stl).