It's not worth it. Buy yourself some 220 grit sandpaper and sand down the red paint. You needn't press very hard. Then, buy yourself a Primer-Sealer. This will Prime the wall for painting as well as Seal the red paint from bleeding through. You only need 1 coat of primer. (Feel free to be just a little generous.) You may need 2 top coats.
I suggest you actually paint the entire wall. If you don't, you will see a 'line' (or a difference) between the work you're doing now and the remaining part of the wall. Buy yourself some Painters Masking Tape. Make sure it says Painter's Masking Tape! If you need more info, post up.
My best to ya and hope this helps.
PS: If it's not too late, I suggest you buy your 'material' from a Retail Paint store; NOT the Home Centers. For a few extra $$$, it's worth it. And if you want to know how much worth it, search the forum for the word: paint and see what folks have to say about painting with 'cheap' paints. Ralph Lauren is one of the BIGGEST offenders.