If you are painting metal railings, get a primer with a rust inhibitor. Otherwise, consult with a hardware store clerk about the best kind of outdoor primer for your project.  Use a small, 3 to 5 inch (7.6 to 12.7 cm), roller to apply the primer on the spindles if they are small but square. If your railings are ornate, you will need to use a wire or sponge brush.    {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/c\/c2\/Paint-Porch-Railings-Step-9Bullet1.jpg\/v4-460px-Paint-Porch-Railings-Step-9Bullet1.jpg","bigUrl":"\/images\/thumb\/c\/c2\/Paint-Porch-Railings-Step-9Bullet1.jpg\/aid2413319-v4-728px-Paint-Porch-Railings-Step-9Bullet1.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"<div class=\"mw-parser-output\"><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/3.0\/\">Creative Commons<\/a><br>\n<\/p><p><br \/>\n<\/p><\/div>"}  Make sure to coat well in 1 direction. Do not leave any excess paint, because you will be able to see priming strokes through the finish coat of paint.    {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/7\/7f\/Paint-Porch-Railings-Step-9Bullet2.jpg\/v4-460px-Paint-Porch-Railings-Step-9Bullet2.jpg","bigUrl":"\/images\/thumb\/7\/7f\/Paint-Porch-Railings-Step-9Bullet2.jpg\/aid2413319-v4-728px-Paint-Porch-Railings-Step-9Bullet2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"<div class=\"mw-parser-output\"><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/3.0\/\">Creative Commons<\/a><br>\n<\/p><p><br \/>\n<\/p><\/div>"}  Allow the primer to dry according to package directions.    {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/6\/67\/Paint-Porch-Railings-Step-9Bullet3.jpg\/v4-460px-Paint-Porch-Railings-Step-9Bullet3.jpg","bigUrl":"\/images\/thumb\/6\/67\/Paint-Porch-Railings-Step-9Bullet3.jpg\/aid2413319-v4-728px-Paint-Porch-Railings-Step-9Bullet3.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"<div class=\"mw-parser-output\"><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/3.0\/\">Creative Commons<\/a><br>\n<\/p><p><br \/>\n<\/p><\/div>"} Use careful strokes in the same direction. Buy a brush that is well sized to your railings to avoid drips from the application of too much paint. This will increase the durability of your paint job. For intricate metal railings, you may choose to apply paint with a paint sprayer. Try to get a small paint sprayer that will reach into crevices. Set up a cardboard shield, if possible, to avoid spraying grass or walls.    {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/8\/8d\/Paint-Porch-Railings-Step-11Bullet1.jpg\/v4-460px-Paint-Porch-Railings-Step-11Bullet1.jpg","bigUrl":"\/images\/thumb\/8\/8d\/Paint-Porch-Railings-Step-11Bullet1.jpg\/aid2413319-v4-728px-Paint-Porch-Railings-Step-11Bullet1.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"<div class=\"mw-parser-output\"><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/3.0\/\">Creative Commons<\/a><br>\n<\/p><p><br \/>\n<\/p><\/div>"} The exact amount of time it takes to dry will vary based on the paint used. Check the label on your paint for an exact estimate.

Summary:
Prime your railings before painting. Apply your finish coat of paint. Allow the coat to dry and apply another coat of paint, if your railings were well worn. Block off your railings and allow them to dry for a few days before using.