How do I touch up large chips in a heavy metal patio set?

It sounds like someone did a layer of latex over the factory finish or didn't prep the metal first prior to painting. All you can do at this point is try to strip it (very messy and pain staking) or have it sand blasted. You have to get the layer off that is causing it to flake and chip. Once cleaned use Rustoleum exterior spray primer, then spray with exterior spray paint.

Yes there is a level of skill for spray painting. The main thing is patience. Do several light coats to cover. Don't try to cover completely with one pass. Spray the underside first. Once fully coated , let dry overnight , flip it over and do top.

I would clean the areas to be sprayed with cheap rubbing alcohol (50%) and

then lightly sand the chip with sand paper glued on the end of a pencil eraser.

Then re-clean with alcohol, spot prime with a 000 camel hair brush, let dry and then spray paint it, as described above.

How I “spot paint”: shake the can very well after pulling off the cap.

Hold the cap away from me at an angle, spray the paint into the cap, enough to make a teaspoon of liquid paint.

Dip my 00-0000 camel hair paint brush into the paint, just the tip, and touch up the small area, filling it in, but not too much, or it will drip.

Be sure & turn the can upside down & clear the nozzle before it dries in it.

Clean the brush with 100% acetone. Form it into a point, to dry in the correct shape.

Hello!

Proper prep is important for good adhesion.

Sanding the furniture to loosen and chippy flaky residual could be helpful.

I like to use the comfort grip or the universal line for effective and comfortable spraying. Perhaps the textured paint made your project more difficult? Might be worth a phone call to Rustoleum for advice or to find out if the product is defective?

As you may be aware, the rustoleum spray paints often has primer and paint combined in one. The universal series has an excellent designed applicator- easy to use top spray nozzle that can operate in any angle. Ive also used the Painter's Touch 2X Ultra Cover on plastic chairs and planters, great results and coverage.

The before and after on my metal mesh patio set was a remarkable accomplishment. See photos below.

Additionally heres Rust-Oleum recommendations for your review:

PREPARE:

Always work in a well-ventilated area. Cover the floor and nearby items with a drop cloth. Lightly scuff any glossy surfaces and wipe clean with a lint-free cloth. Use Painter’s tape to hide any surfaces you don’t want to paint.

PAINT:

Using slow, back-and-forth motions, spray paint each item with several light coats of spray paint, making sure to overlap each stroke slightly. Apply 2-3 coats of spray paint, waiting a few minutes in between each coat.

FINISH:

Let spray paint dry for approximately 1 hour before handling.

Tip: Use of 2X Ultra Cover Primer in White provides better paint coverage and color.

You probably should have used a metal primer first. Sand and clean it off and prime and then spray paint with your Rustoleum. Light coats are better when spraying and it will take more than one session to do a nice job.