On a 136 the process is usually this:
you get positive skills buttesment letter (from tRA in your case)
you fill in 47sk + post it , along with full copy of what you sent the TRA, plus the tRA letter, Plus a ton of other tihngs
they send you a letter back saying ' please forward PCC(police check) and Medicals (and they send you aform for medicals - it is a special form non downloadable) ' you get both done and send them back.
There is a 12mth expiry on pcc checks and meds which means - they are invalid after 12mths so they potentially set a 'must validate by ' date on your visa - but since you are in Aus thats a bit irrelevant - it really means you need it processed in less than 12mths or they expire.
Sending Meds + PCC's up front is call front-loading if oyu serach the forum for this you'll get advice.
If you've got a Positive TRA you do not need an agent mate.
You can download the 47sk now and look at it along with booklet 6
I'm not sure what nuances they put on it for applying from a 457 and actually being in Aus when its granted - but if you rnig dimia enquiry line they shold help .
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