djreiswig,
since you need the process only one time when the start button is pushed then stop and wait until its initiated again, its not so difficult for you to use relays for this job, see the attached ladder logic diagram, it shows how you have to wire the relays and its contacts to get the required operation.
hope i dont want to explain how it works, you have to wire the relays, even different voltage levels can be used.
if some relays are not having enough number of contatcs they can be miltiplied by an intermediate relay.
Edit: small mistake modified. for mixer, you have to use a timer and trigger it when the tank gets full, stop it after 5min.