Several ways to do this, here's what I do, ( but note, templates are not symmetrical side to side, so some minor adjustments will be required ) multiple layers for your design will need to be done in two ways, duplicate each layer one at a time, hide the original layer, turn on wire mesh layer, High-lite the new duplicated layer, ( I place a 10 pixel square in the bottom of that layer using the wire layer as a guide, bottom right skirt area in the corner where the wires are straight) now flip that layer vertically, then move it to the other side using the square to align it up correctly, square should be in same place in the wire layer. Do this for each layer you have a design on, time consuming I know, but if you use the pen tool to create these designs, it will keep that so you can make fine adjustments if needed.
Second way I've done this is almost the same, but I merge all the design layers together ( I use the pen tool, so I convert this one layer to a rasterized layer, then duplicate this layer, move to other side.