I have tried to sign a Wr coach every transaction period so far and am 0-5. At least twice I was offering a much better contract and the coach signed elsewhere for less money to be an asst. coach. This last period I offered a 3 yr 13M contract to this guy
http://mfn19.myfootballnow.com/coach/542

but he signed for less money for the same role on another team.

What gives?

Find a position coach that isn't better at another position. Look down the list. If you're looking to sign a WR coach who's like a 70, but an 85 at O-Line or DC, someone is going to pay a lot for him to take that spot. Sign a bad coach at low cost, then try to upgrade from there.

That doesn't explain why coaches are signing elsewhere for less money. Twice I have offered more money for equal positions, yet the coach signs elsewhere

An unemployed coach should sign the best offer on the table unless you don't have the cash flow to pay him.