For reading comprehension, speed is not the most important.
In my opinion, the most important technique is to get as much information as possible in just ONE reading (since you probably do not have much time for second or even third reading.)
Please note, there are 4 RC passages, thus, they should be short, so, try to remember the details of the passages, (as you go through OG10 and OG11, you should discover that a lot of questions are about details of the passages.)
Practice is the key, apart from OG, try 1000 series, or GMAT+ or any past papers from LSAT, and GRE, Also, any older editions of OG you can find in the university library or public libraries should be helpful, too.
If you have time, try:
By the way, what is 800 score?
how can I get such material?