Have a look at the modeller.parallel module and friends:

http://salilab.org/modeller/manual/node69.html
http://salilab.org/modeller/manual/node408.html#SECTION:parallel

As an example, you need to have something like this:

from modeller import *                      # Load standard Modeller classes
from modeller.automodel import *            # Load the automodel class
from modeller.parallel import *             # Load the parallel class, to use multiple processors

j = job(modeller_path=os.path.join(modellerPath, "bin/modslave.py"))
j.append(local_slave()) # 1 Processor
j.append(local_slave()) # 2 Processors
j.append(local_slave()) # 3 Processors...and so on

env = environ()
..... Regular Modeller definitions.....

a.use_parallel_job(j)                        # Use the job for model building
a.make()                                     # do the actual homology modeling

Regards,

João [...] Rodrigues
@ http://stanford.edu/~joaor/