Police say they've made "significant progress" in building "trust and confidence" with gun owners.
More than 61,000 firearms were surrendered in the buy-back and amnesty scheme.
The Auditor-General found the collections were carried out with empathy and respect.
Police have now published a follow-up report.
It says they have worked with gun owners to rewrite weapon safety and storage guides and test a new police firearms website.
And it says they have partnered with dealers to set up an online licence check.
The report also stated police have maintained relationships built through the amnesties.
Overall the report says police has made "significant progress towards improving engagement with the firearms community" in response to the Auditor-General's recommendation to "strengthen relationships and build trust and confidence" in firearms regulation.
Northland's Antique Arms president Kaleb Smith agreed police had helped firearms users adjust to change.
"They are making efforts. I've got several friends who are gun dealers, who they have actually outreached with and tried building a relationship personally."
But he told RNZ there were information gaps about how the new firearms register will work next year, and current gun licensing delays.
"You have to apply months in advance of the expiry date, which kind of defies the point of having an expiry date. So if they sort of just knuckled down on the way that they're going about their licensing process, that would actually take a lot of stress off firearms owners."
Police admit it is taking six months to renew licences and a year to process new licence applications currently - because of Covid-19, and tighter vetting rules.
They have more than quadrupled the number of support staff helping process applications, from 14 to 63, and expect delays to stop next year.
But Smith said last month's theft of firearms licence records from the former Auckland Central Police Station had eroded trust.
"If there's a registry, it's just asking to be taken advantage of by people who shouldn't be having guns."
One licence holder, Jay, told RNZ he handed in a military-style gun during the buyback that he had used to kill goat, pig and deer pests on a farm in Te Tai Tokerau.
He rejected the police progress report.
" totally disagree. We've just been shit on."
With the guns he uses now, he said it was harder to stop animals suffering.
"We get by now but it's painful, it's just painful to watch. If you did wound that animal [before] you could finish it off. Sometimes, now, you might get two shots away."
Fellow firearms owner Ernie Wilkins didn't agree with the buyback scheme - he thought it mainly involved law-abiding people, not people using guns for crime.
"Police haven't got an easy job that's for sure, but I think they need to get a lot tougher on gangs."
And he was concerned the licensing waits, and extra checks involved, were discouraging people from following the rules.
"The paperwork is just horrific now and it's not really achieving anything. Just keep it simple and keep it straight. Give people confidence in it. People now are just getting that fed up with it, it will probably drive law-abiding people to say 'well to hell with it, I won't even register my firearm'."
But police said in the report that the buyback scheme, and firearms registry, were reducing the risk of harm.
National coordinator of the Islamic Women's Council, Aliya Danzeisen, said the reforms since the 2019 mosque terror attacks had "definitely" helped safety but there was more work to do.
"We see today people are still getting shot in New Zealand, so it hasn't cleared all the concerns related to all firearms usage, but it has taken a big step and definitely we are safer."
She said: "People will now not have weapons they can kill multiple people [with] in a very short period of time, and that prevention is really important."
She also said: "Rightful users that are using them [guns] for a hunting purpose or recreation in a safe manner - we don't want to to prevent them from those types of usage."
This year's Budget set aside $208 million, over four years, to establish police's new Firearms Business Unit, which will oversee the incoming firearms register.