Summary - Lookout is drive up with a wide open summit, though parts of the way up aren't for the faint of heart. There is a small comm facility that doesn't generate appreciable RFI, a couple of places to set up, and when the clouds aren't in the way, excellent views. Bring a mast if you want to put up a wire. 2M contacts are possible with a 1/2 wave whip but a yagi will make things a lot easier. APRS is easy from here, too. Drive time from SE Portland is about two hours through Stabler and out Hemlock Road (turn at 45.80838, -121.90741).
TL;DR - Lookout is part of a cluster of SOTA summits -- D layer, Continuity, and Green Lookout -- that are reached by way of Hemlock Road in Stabler, WA. There are other nearby mountains, including Mackensie Ridge and Green Lookout, that are probably accessible from Stabler but I haven't driven all the roads up here (yet), so YMMV. Lookout is a drive up as long as you are prepared for very narrow roads (particularly the approach road to the summit, 501) with steep dropoffs on one side. If that sounds sketchy, park at the start of 501, and hike the last section! Here is a gpx route from Stabler to the summit, in two parts:
Stabler to Lookout Mountain GPX files, LC-066
Once on top, you will find an open summit with a small communications facility that doesn't seem to generate much RFI. There are places to set up on both sides of the summit but no sizable tress. Bring a mast if you want to put up an antenna. Pro tip: be prepared for foul weather and wind. Though it was August, I was happy I had a knit cap and thermal shirt in my pack during my activation. I made 2M contacts with a half-wave whip but things got considerably easier after I set up a three element yagi. Two way APRS messaging worked well but ATT cell service was hit or miss, mostly miss.
Lookout would seem to be off the beaten track but I wasn't the only one on the summit that day. Though I arrived quite early, there was a pickup truck in one of the two parking spots and during the day, two motorbikers and one Sprinter van showed up. There were also several groups camping on the road below the summit. Given the likelyhood of encountering others on the narrow road and the paucity of turnout spots, take care while driving.
All in all, this is easy drive up summit (if you have 4WD) that I recommend putting on your WA list.