Something I learned from an RN a few decades ago. First, take a soaking bath up to your arm pits in very warm water for about 20 minutes. Place a soapy washcloth under each arm during this time, but rinse/wring them out about every 5 minutes. Then reapply. Do a rinse off thoroughly with warm-almost-tepid water. You don't have to scrub. The soaking and warm, soapy water will work for you.
The other day I posted a note about the BEST deodorant I have ever used, and it is still true. Dentarome by Young Livng. I ordered some online. It doesn't contain sodium lauryl sulfate (sls) or fluoride or silica. It says it's "All natural, germ-fighting toothpaste fortified with Thieves Oil."
A dot about the size of a small pea is enough for both underarms. It tingles just a little for a couple of minutes, but the deodorizing lasts until the next day. I like to apply a puff of powder after I apply my deodorant.