Eighteen years ago when Jersey European Airways first got their Dash Eight 300s they put Captains into the LHS who had only flown single crew King Air ops and had no major problems.
Any new Captain will do 100 hours on type after line training before being allowed to fly with new F/Os with less than 100 hours on type. That's all it needs. The operation is still basically double EDI or double GLA or EXT GCI JER. It's not flying the Atlantic, and as has been mentioned it's not rocket science either, even if the Q400 is a bit faster than the 300.