just to get it clear before layouting for some time for nothing.
First of all, i think vias automaticaly get connected through from layer 1 to layer 2, right?
Then my question is, what are good dimensions? I do use at the moment round 0,7mm outer diameter with a drill of 0,4mm in it. Is that possible for you?
Besides, what is the average/minimal size of vias you can handle?
When using the Seeed .DRU-file for Eagle the default via holes are 0.3mm with a 0.6048mm pad, they seems do be handling that size just fine. If I need more current handling capacity I just add a few more vias there or go up to a 0.5mm via.