by solo do you mean like home gym, or just not with a partner? if its the latter, just learn to break that shyness and ask for a spot on your heaviest sets. eventually youll find 2-3 reliables that wont spot like a jackass and work out the same time as you
you also gotta realize that strength and power are two different goals. strength revolves around max load movements like bench press variations.
power involves max velocity movements, think of sport related or being able to push someone/something out of your way. which one do you really want?