Summary - A short but very steep scramble up game trails will get you to the top of this very visible summit in the Toutle Range. Combine it with 4562 and Castle Peak and hit Signal Peak on the way out to make it a four summit day. ATT and APRS are good. Don't count on two meters. Be wary during hunting season and don't attempt the summit hike when the weather is poor. See my 4562 trip report for driving info.
TL;DR - Spud Mountain is the first of three SOTA summits at the end of the Toutle Range, about fifteen minutes from Castle Peak and thirty from 4562. Spud is a steep-sided cone and easily recognized from any of the local high points. The summit road begins at 46° 14.92', 122° 19.55' and ends at the ridge you'll climb to the top. You will go straight up the nose of the ridge (the grade is roughly a steep 30%) along a user path that soon dissolves into a maze of game trails. Pick your way up and around several small band cliffs to gain the summit; don't veer off the nose! This is definitely a class three scramble the whole way and I wouldn't try it in the rain or snow.
At the top, you will be rewarded with views of Mount Saint Helens, Mount Adams, Mount Rainier, and Mount Hood. The summit is open, unshaded and covered in manzanita and bear grass with sharp drops to the valley below. A mast is handy but you will find a few trees for hanging wires. Don't count on two meters. ATT and APRS service is good.
If you are comfortable with steep scrambling, this is a very nice hill to combine with Castle Peak and 4562 (both of which you can see from Spud). As with Castle and 4652, the hill itself is striking, the views are terrific, and it provides a comfortable, though shade-less, spot for a longer SOTA session.