Cleaning/Stripping advice

We stained our new deck a year and a half ago with one coat of Armstrong oil based semi transparent Rustic Brown. We loved it and has held up well.

We are going to stain the deck again and looking for the correct prep. They deck gets a fair amount of sun so no mold or gray on the boards. Do we need to strip, clean, sand or all the above? We are going to use the same Armstrong stain and color.

Also, I read on your site that you only want one application of stain on your new deck. Since this will be the second time staining, can/should we apply two coats this time?

Any advice would be helpful so we can keep the deck looking good.

Thanks!