If you want to space eg. two single tracks to make a double track, an easy way is to use what we in the UK call level crossings, which I believe in the States are grade crossings, You can use one appropriate to the track spacing for the country you are modelling (for me in the UK that's 3.5 metres, but wider elsewhere), lay your tracks to/between the crossings, then delete the crossings. I have done this, also using a very short length of fixed track attached to the crossings before deleting in order not to lose the alignment.
Ray