I see noone is answering your question directly. So here it is.

Use a freelancing service and have them do certain technical tasks. Strike up a conversation to check their communication skills. Check the quality of their work. If all good. Ask if they are interested.

I have two technical cofounders. As ppl rubbish the idea. I get three times as much work done. Faster to market. Solve problems I couldn’t have otherwise and you are right, investors want to see it.