Welcome Daniel.

I am also currently building an ES-1 and they are a nice kit. Timber on the back of mine has a very stringy grain that easily swelled from using water based stain and the front horn lumps are easy to sand through if not paying attention. Best not to do much sanding on the quilted top as the veneers seem to be thinner than a piece of paper. If using a stain best to have a really good look around all edges where binding is attached as there is usually some glue spots that need some attention or removal to allow any colour to penetrate.

Cheers, Waz