I completely share your pain on this because I just recently attached bugnetting to my double layer. There is no easy way to do it like I wanted it done. I sewed my bugnetting down between the two layers of ripstop on on side of the hammock. This creates one major problem. You cannot sew the other side until you determine the lay of the hammock, which invariably results in more bugnetting than you need on the other side of the hammock.
So there are two things you must determine before a good course of action can be chosen. Do you want the bugnetting between the two layers of RS or are you okay with simply stitching the bugnetting down to the top of the RS???
If you want it between the two-layers, get ready for some headache. Let me know if this is how you want to do it and I will give you some pointers from my very recent experience doing it like this.
If you are okay with just stitching it down to the top or bottom of the RS, then do what everyone else has suggested. Have someone lay in the hammock that is pretty close to your height and stretch out the netting and begin pinning.