Wood Siding Install
The condition of the wood siding will decide how the installation of the injection foam is done.
If the wood is in good condition, it can be removed, and the holes would be drilled into the sheathing underneath. Once the installation is complete, the holes are plugged, and the wood siding is replaced.
If the wood is brittle, there is the chance it could break, so it makes more sense to just drill through it.
In both cases, the actual injecting of the foam is the same as vinyl or aluminum siding – the hose is run from the top to the bottom to ensure the foam completely fills the cavity.