Hi Carlos,
We backpacked summer 2018 in Denali, during late August. We had permits for a total of 5 nights, Unit 12, 13 (two nights), 18 and then back to 13. We hiked down from the Eielson visitors center on a trail and then into Unit 12 essentially by following the Thorofare River, either on the river bed or the bench above it. Crossed into Unit 13 via Contact Creek (passed the backside of Mt. Eielson) and then down Wolverine Creek. We were unable to hike into Unit 18 due to heavy rain and more importantly fog (couldn't see much and didn't want to surprise any bears) but Unit 18 can be accessed via Glacier Creek. We hiked out via Glacier Creek and the bench above it, crossed the multiple braids of the Thorofare and back to the Eielson VC. Map and compass are essential as is being able to match the terrain you see with what's on the map. I've done a lot of backpacking and those 6 days, although not long in distance, are one of the highlights of my hiking career. Awesome views (saw the mountain one beautiful morning ), Muldow Glacier views are amazing, lots of wildlife (mainly grizzlies and caribou and one golden eagle that I swear was only 20 feet above my head) and of course, lots of rain. We had 30 straight hours at one point and the whole hike out was a washout. But, since we ended at Eielson VC it was easy to change clothes, warm up and get on a bus all in quick order. You might want to check out a book by Ike Waits about Denali hiking and photography. He has some good descriptions of navigation in various units and we found it helpful.