How do I easily fix spillover after painting stripes on my walls?

Using the blue painters' masking tape. mask off the portions of the stripes where spill overs took occurred. Assuming the striping is well dried, be sure to firmly press the tape at the edge of the stripes.Then, using base coat, paint over the space between stripes where run over shows. Don't worry if a first coat doesn't do the job. Just add a second coat. The base coat paint should be thick enough to not easily run and brush paint horizontal with or away from the tape, never towards it. Good Luck.

You do not need to scrape the walls. The product you need is called Kilz, which is available at Home Depot, Lowe's and other home improvement stores. Be CERTAIN that you get the acrylic (water-based) type. DO NOT get the oil-based Kilz. Paint your walls with a coat of Kilz. Let it dry, and then determine how well it covered. You may need two coats of primer. (Red is the most saturated of all the colors, and is therefore VERY difficult to paint with, and almost equally as difficult to cover up completely.) After you've primed and let the primer dry completely, you're ready to paint. Use a good quality paint (I prefer Behr, but most painting contractors prefer Sherwin Williams). You may need two coats of paint--again, depending on the shade of red you're starting with.

Get a small artist's type paint brush and carefully paint over the mistakes.