Shastina is a rather miserable hill next to Mt Shasta and it is a rather
low one by comparison (3758m) but it might take you longer to climb Shastina
than Shasta because of the endless and very loose scree. Recommended only
to masochists who have a lot of patience.
From the Bunny Flat trailhead hike to Horse Camp and then look for the fork to Hidden Valley. It is very easy to lose this trail and very easy to lose it on the way back, so mark the territory. Once at Hidden Valley the big mountain in front of you is Mt Shasta (or better the Cascade Gulch that leads to Misery Hill that leads to Mt Shasta) and the mountain on the left is Shastina. It is a straight climb to the top. The snow usually melts early on Shastina. In early summer you might have to cross a field of snow to get on the slope that leads to Shastina, but it is mostly flat.