Repaint metal railing

First advise is not to use any "sealer" on window frames. Paint won't normally adhere well to wood sealers. If possible, I like oil based exterior primer, even two coats so your frames are well covered. The you can use any good latex exterior trim paint. Remember, prep is very important, and you cannot use oil based primer over any latex, so if you have latex, you must use latex primer or BIN's Bullseye pigmented shellac.

Good question Nick. I manage several rental units and have dealt with the same situations. Originally, flat paints were used in most of the rentals and almost every couple of years they needed repainting especially if kids were in the unit. Flat paint is hard to wash and very susceptible to marring and finger prints etc. The newer flat enamels are better, but not great. I changed over to a harder eggshell finish. Depending on the time a tenant is there, the eggshell really outlasted flat, usually good for 3 to 5 years unless damaged. Satin enamel works great for ceilings, hides marginal imperfections and very easy to clean between tenants. I have also found that since looks is more important than durability, I have used a lot of PVA grade wall paints from Ben Mor. At contractor price, it can be almost half as expensive than premium grade paints, covers well, lasts for several years. I have given up on expecting paints to be show ready after a few years in a rental. Cleaning and touching up walls takes almost as long as painting so a new quick same color wall paint job between tenants freshens up the place and smells new when showing the apartment. I tend to use just a couple of colors for most everything, so I buy 5 gal cans for economy, batch small leftovers and treat older paints with Flotrol. Be sure to keep the color formula in a notebook (ask for an extra sticker) so you can buy a good match later. Changing colors always requires two coats, but one coat of same color is normally fine. You can use your leftovers with new paint if you strain it through a mesh colander and batch it with your new paint, thus slight color changes disappear.