Get some pre stain. What I do is go over they whole sheets when i by them with the stuff and sand them off a bit. After this the blotchy stuff will be a thing of the past. Its just this white watery looking stuff you brush on, let dry for a few minutes, wipe off and sand. takes 15 minutes max and works great. i think its called minwax pre stain of something like that, a quart will last you for the rest of your life basically.
got this tip from a guy who used to build high end furniture so it works.