I prefer the pan head screws made especially for these joints.  I find that flat head screws (I don't use bugle head drywall screws) can split out the wood when applied parallel to the grain.I find the Kreg Mini a good choice, especially for repair or reinforcing existing work.  Less than $30 with a box of screws and a cheap clamp and you're good to go.And if you don't need disassembly, put in some glue.