primer orange peel
A few suggestions that should get you spraying orange peel free
First off, 1.8 is kinda big, better word is it's huge. I'd suggest using a 1.5 tip.
Here's a few tips that work at my shop.
Set you wall regulator to 100psi, this should give you the cfm that your gun requires and with out the added pressure drop. Next set the micrometer at the gun to factory specs with the trigger fully pressed and fan wide open. Next your going to set your fluid needle's volume. Completely back out the volume adjustment screw until it comes completely off, then just start the screw back in so that there is now pressure on the needle's spring.
Next fully trigger the gun (of course with it disconnected from the air line and no material in the gun) and start turning the volume control screw until you feel pressure on the trigger. This is what you call a full trigger which most guns are designed to spray at.
Now for the test patter test. The rule of thumb is 8x8. 8 inch fan and 8 inch distance from what your painting. With the gun fully loaded with paint, and using the 8x8 rule, which at this time don't mess with the air setting that will be later, full trigger the gun and close it. This should be a quick movement. Now inspect your spay pattern. This spray pattern shows everything. runs, dry spray, everything if you know what to look for. The major cause of orange peel is to much material incorrect reducer/thinner, and air pressure.
Never get in a hurry, and never try to have complete hiding with one coat. Way to much material. We usually have complete hiding by 4 to 5 coat. Nice light coats is all you need. Now there is a difference between light and dry. The paint shouldn't feel or look like sandpaper If it does then drop your air pressure by 5psi and shoot again. If you experience runs, increase the air pressure by 5 psi. If it still runs then close the fluid needle in 1/16 of a turn increments. Most of the time you don't want to go under or over the factory specs more than 5 to 7psi.
Now with the reducer and thinner, follow the P sheet for the material that your using. Don't become a chemist, that is what you paid them for. Now once again there is an exception to every rule, Use the lowest possible temp range that you can get away with without causing runs. So if your shooting during the winter try a normal reducer instead of a fast reducer, but mix the stuff according to the P Sheet. And one more thing, don't expect to get a great performance from cheap materials.
Hope this helps out