For drawing the vias:
- Set your design rules for a realtively thick tracewidth & via diameter.
- Make sure there is no solder mask over the vias (So they get filled with solder).
While drawing a trace (use 'x' in PcbNew) every time you press 'v' you switch to the other side of the board, and if yo do that during drawing a via is automatically added.
Draw a bunch of vias in a grid like this:
If both sides have a polygon then your vias and the traces will automatically be a part of it.
Another very quick way for drawing lots of vias is by right clicking on a via and select "create an array [Ctrl +N]"
In PcbNew there is an option to clean the pcb a bit with:
PcbNew -> Edit -> Cleanup Tracks & Vias.
This function might remove a lot of your via efforts but it might be worth experimenting a bit with how it works and could be usefull for you.