Is this Red Cedar OR White Cedar. Red Cedar ..is more expensive but should always be painted. It will last forever.
White cedar can be bleached or allowed to weather. Looks like
Cape Cod "weathered".
Belt sanding..??? NOT what I would do. Pressure washing..NOT what I would do. If there is an old coating on the wood..Varnish..etc. Strip it with a hook scraper..By HAND..OR Chemical Paint stripper. Anything else
Removes TOO much Wood. Not good.

NB
BTW: Varnish looks nifty for about 3 years. Then you need to strip it and do it again. Unlike Paint...you just can't lay another coat of varnish on top of the old weathered varnish.