Special preservatives to protect against termites, carpenter ants, insects, rot, mold and mildew
One aspect of preserving wood is preventing wood destroying organisms from attacking the wood. All preservatives are made to stop nature's biological process, so proper precautions with regard to handling, application, and proper disposal of containers is very important. Follow the manufacturer's cautions and consult the MSDS (Material Safety Data Sheet) for special precautions.
Most preservatives offer some type of guidelines to the actual life expectancy of the product, but as a rule of thumb, you can expect two to four years before a reapplication is necessary.
Conventional methods used to apply stain or finish may also be used to apply many preservatives. While they may not require the brushing, they can usually be sprayed, rolled, or brushed in the same way you would apply finish. Make sure you follow the recommendations that are on the label.
We now are marketing a dual purpose preservative that offers several benefits to the homeowner. One problem with not having a preservative, which is associated with white pine lumber, is the development of Blue Mold, or Blue Stain. Customers complain that wood is dark streaked or moldy, and bleach will not remove this condition. This stain actually starts inside the wood and is difficult to kill from surface treatment alone.
Use Shell-Guard for the protection and preventative treatment of wood against termites, carpenter ants, wood destroying beetles, wood decay fungi and for remedial control of such pests in infested wood or wood foam composites. Apply the solution of Shell-Guard by brush or spray until surface is thoroughly wet (1 gal per 108 square feet).
Application may also be made by drilling and then injecting the solution under pressure into sound wood or until run-off is observed from entry/exit holes of infested wood. Treatment methods as described yields an approximate retention level of .24 pounds per cubic foot boric acid equivalent (BAE) in the outer 3/4" of the wood.
To minimize borate leaching apply a water resistant sealer such as Lifeline Ultra-2 or Lifeline Exterior after the surface is dry to the touch - in low temperature and high humidity locations this may take 1-4 weeks.
That will bring you to STEP 3.
Stains and Finishes Application Guide 
Application Guide for Lifeline stains and finishes
Log Home Sealant Application Guide
Application Guide for Perma-Chink, Energy Seal, Stack-n-Seal