For me, power came from singing (leading) chorus songs and needing to be just a little louder than the chorus to help them keep time.
When I started with Mudcat singarounds, I could manage maybe 2 songs before aching too bad to sing loudly, but like most muscles, you can
work on the technique over time.
Remember, though... Not all songs are suitable for singing with a strident voice. For example(s)
Stuff I have sung/sing loud:
Ale, Glorious Ale
Fathom the bowl
Ye Mariners All
Thousands and more
Stuff I have sung/sing for clarity, but cannot exceed a certain volume due to the ornamentation:
Fields of Greenmore
On yonder hill there sits a hare
Hope this helps - and keep practicing.
Don't worry about sounding less than Pro - /the songs are pretty enough to cover it up ^^