Hi, my name is ***** ***** I have been in the home improvement and repair field for 20 years. I will be glad to help you today.
As far as the ease of getting the gate to not get the moss on it will depend on the tools you have. If you have a pressure washer (and depending on how hard it is to get the moss/algae off the gate) will determine the difficulty level.
First you will trim back any bushes or plants nearby and cover them with a tarp or upside down bucket or whatever works so that they can be protected.
Then power wash on low setting and remove what you can that way.
Once the fence is totally dry and there is not any moss or stains then do the next step but if there is more stains you will have to hand wash and let dry.
Next fill a bucket with 1/2 bleach 1/2 water and wash the gate. Scrub any stains that remain.
Let it dry again and sand any uneven areas and sink any nails.
And last apply some wood preservative,stain or paint with some algae and mildew preventative.
Great. Many thanks for that information. Any suggestions as to a good (easy to apply) wood preservative please? I really want to just 'slap it on' and not have to mess around with a paint brush all day. Thanks!
Really all of that is up to you. Colour and type are all related to what is your taste. If you would want to stain or paint can be determined when you are in the paint aisle at the store.