[wvguy]

the semi transparent has been on there for a year so you are ok to cover with a solid. However, I do not recommend using a pressure washer for one big reason. If you pressure wash you will loosen wood fibers to when you apply a solid color stain you run the risk of it peeling. Easy answer, use a good quality deck cleaner and rinse with garden hose, allow to dry for 3 days is a good idea then stain. Most solid stains on the market will require a primer. There are a few out there that will not, they will be self-priming such as the Olympic DFS Maximum. I advise using one that is 100% acrylic latex this will allow the stain to expand and contract with temperature. Use two coats and you will be set.
Solid color is great for an older deck to cover up an aging deck.