[phenixbb] Refinement with partial model - question

Dear Phenix Users, I have a partial model at low resolution. Is there a way let Phenix.refine know the model is not complete and that when a mask is calculated for bulk solvent correction it should take this fact into consideration ? Alternatively, can I use a solvent mask from density modification program in Phenix.refine somehow ? Alternatively, is there a program that will build dummy atoms (zero occupancy) automatically in a map in all peaks above a certain sigma (i.e. atoms just for mask calculation). Thank you in advance, Peter.