Hebrews 5:8,9 is speaking of Jesus, not us. in the devotional you read, it is a half sentence taken out of context - taken in context, it is part of a series of scriptures that explain that Jesus suffered temptation the same as we do, yet did not sin. this is not saying that "God can use the pains in your life to help others."
God doesn't need to use pain - He has given us His word and His Holy Spirit to teach and guide us. pain may get people to shift their focus from themselves to God, but it is not God's way - His way is to instruct us through His word and lead us and and comfort us through the Holy Spirit.
2Ti 3:16-17 KJV
(16) All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness:
(17) That the man of God may be perfect, thoroughly furnished unto all good works.
this does
not say 'All scripture
and pain is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness...'
1Jn 2:26-27 KJV
(26) These things have I written unto you concerning them that seduce you.
(27) But the anointing which ye have received of him abideth in you, and ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in him.