The emulsified oil stain is a good choice, oil/acrylic mix. The ones I have used in the past have performed well, better than a straight acrylic stain.
Preparation is the same for any type of exterior house staining job.
1) Wash to get a clean surface and remove some or most of the old stain. The full extent of the washing depends on the condition of the old stain.
2) Allow a few days to fully dry. Very dry wood is very important. If you have or use a moisture meter you want 10% or less moisture.
3) Apply the stain liberally. You don't want to under apply the stain. Often 2 coats is a good idea.