Hi! It is much better to keep the two piggies in adjoining cages so they have each their own territory, but can interact through the bars, keep each other stimulated and company, and get to know each other better over time.
THEN you can start mingling scents. Without knowing where the scent comes from, a piggy can feel invaded.
Scent mingling is fine in the advanced stages of an introduction run-up, but not when the piggies cannot meet ea\ch other in person and become more relaxed with each other.
In the end, whatever you do, it is all down to whether the piggies like each other and get on. No trick in the world can make somebody like the other and be good friends unless they do it themselves - that goes for humans as well as guinea pigs.
So it is better to give them the opportunity to meet through bars and get more comfy with each others' physical presence, apart from the fact that piggies need company much more than us. Even if the bonding doesn't work out, just having a neighbour they can interact with will keep them from becoming depressed in the longer term.
When I let my own piggies sniff other group's stuff, it is always on neutral roaming ground.
