How long for rests? Generally 10-15 min for the lower temp rests and at least 30 for your main saccharification rest. If you do multiple sacc rests, go longer on the one that favors the wort fermentability you want (lower temps = more fermentable). Higher temp sacc rests take longer than lower, so they should be longer if you want them to do something meaningful.
You can step by infusing boiling water, direct firing the mash tun, or decocting. Depends on your system and goals. Infusing is easiest, but you should start thick. Direct firing is what I use most often, but I can recirc my mash tun with a pump. I'd worry about the temp being radically different at different layers of the mash without that approach. Decocting is a step mash, and is good if you have the equipment and time. It gives other flavors, darkens the wort, but doesn't really change your overall mash thickness, if that's a concern (capacity and such).