You always have the right to hire an attorney for any criminal proceeding.
But if you cannot afford one, you only have the right to a public defender if you are making a motion to withdraw your guilty plea before you are sentenced under CrR 4.2 and CrRLJ 4.2, not after you are sentenced.
Why is this?
Under the Sixth Amendment, you have the constitutional right to an attorney at all “critical stages” of your criminal case, and sentencing is (obviously) a critical stage. That's why you have the right to a public defender for a CrR 4.2 motion.
But under Washington law, you do not have the automatic right to file a motion to vacate your guilty plea after you are sentenced. Therefore, under Washington law, a post-sentence motion to vacate your guilty plea is not considered a "critical stage" of your case, which means you do not have the right to a public defender.
If you cannot afford an attorney for this stage, you will have to hire a private attorney or (if you cannot afford one) represent yourself.