Whenever I have to answer the call of nature at a public restroom, I utilize a simple procedure. I carry a glock 19 IWB (Blade-Tech) with two mags in Blade-Tech mag pouches (held with a Blackhawk! 1.75" belt). After selecting a suitable stall and locking the door, I unfasten belt/trousers and then refasten the belt in a lengthened position. The secret is to have a belt that is long enough to allow you to refasten it so that it makes an "unbroken circle" large enough to lower it past your hips. The velcro on the Blackhawk! belt works great for this, but leather belts can be used, as well. Next, lower the trousers/belt to mid-thigh, applying mild outward pressure with thighs to prevent the weight of the gun from automatically lowering trousers. I then lower underwear rolling said skivies outward so as to cover the grip and mags. I then lower trouser/firearm/underwear assembly to ankles and proceed with the task at hand. The underwear (boxer briefs work well) conceals the gun/mags. Mild outward pressure can be applied with the ankles to keep the gun/mags vertical. Personally, I think that removing the gun from your immediate person (whether in the holster or not) is a bad idea.
Some folks have irritable bowels. Unfortunately, mine are downright angry. As such, I have personally logged countless hours in restrooms throughout the south perfecting this technique.