I'm not following you; what makes steaming skim milk hard? The texture is more airy, but that is to be expected without fat. Inject very little air by burying the tip deep sooner. What am I missing?

Marc's right. Good steaming power will roll the milk along the bottom and back up other side like this:



If your machine can't do this, one post-steaming trick is swirling/thunking to combine the liquid and foam. The video below is one of my "cotton ball" goofs that I partially recovered from using this technique:



Technical commentary copied from another thread: For a latte, too much air was injected, though it was about right for a cappuccino. I used my largest cup (12 ounces), which drew out the espresso to a thin layer, increasing the speed with which the crema dissipated. The polishing technique seen in the first part of the video eliminated the "cotton ball" and elicited a nice paint-like texture from the milk. Pouring began high, though not aggressively enough, causing an initial splash of white across what little crema remained. I should have lowered the pitcher nearer the surface and the rocking motion was too late and not quite enough.

It helps if you use a pitcher that's slightly larger than needed. This gives you the extra height to swirl the liquid up against the sides, thereby incorporating the foam. Some find it helpful to place the pitcher directly on the countertop and move it in a circular pattern with two hands; it's easier to swirl more aggressively this way without spilling.