Thinning second coat of stain

Hi, first post here. I stained my front porch this weekend with Behr semi transparent deck over stain (colored a darker brown). I only did one coat and it has dried into a nice color. I want to do a second coat to even out some areas and to smooth out some brush strokes (I mistakenly used a brush on some parts not the pad) and give it the protection it needs, but I don't want it to end up significantly darker. - to where it looks like brown paint. Is there any way to add a second coat but have it go on lighter? Can I use paint thinner or water to thin it a bit but not change the color? What is the best way to measure that if so?? Any insight would be helpful.