I have two portable units I have used for brewing for years. One for the HLT, and one for direct fired mashing. I wrap the mash pot in 5 layers of reflectix (metalized bubble-wrap). It holds the heat very well so I don't have to apply any heat at the various rest stages. I made a foam lid for my mash pot to hold the heat better. The HLT is wrapped as well, but only has it's original metal lid
I turn the heat on my mash water (typically 3 to 3.5 gal.) and by the time I get my grains weighed and milled, the water is just about ready . I do use a lot of pilsner malt so I am often mashing in at 122 F.
Step mashes are a breeze. My step rate is about 2 F per minute. My normal steps are 122, then 147, then 160, and then 170. I vary the times at each temp. depending on the style (crisper or fuller)
I don't bother with the heating settings. I run the mash tun unit full tilt and turn it of once I've reached the rest temperature. I run the one for the HLT on med-High as I find that get's my 5 gal of sparge water to ~170 by the time the mash is done
Oh, and you can't use the commonly available wired probe thermometers (at least the ones I have). I think the magnetic fields being generated by the coil mess up the signal being sent to the base unit. My simple all-in-one unit appears to be unaffected (no connecting wire)