no polishing
i use a 2mm tip for acrilyc and it comes of the gun without needing to rub it back and polishing it but i do any way 1.8 will be fine
that's about how I do it I've painted heaps of dunger repairs in that method a door or a guard , never cut and polish any of them a couple of nice wet coats or paint then a clear wet coats also , I all ways seam to add a little extra thinners I mostly use concept acrylics
when I say wet i don't mean pour it on to the point it runs you'll have to rub then no wooden knees, and no runs
while your playing with the air settings I use around 60 psi play with thinning the paint down while your practising I like it to just drip off the stirer