Regarding the sweep process, there are some issues with counterwallet however, we found an alternative confirmed by the counterParty community :
https://github.com/Jpja/Sweep-XCP-PaperwalletJust ensure that you put the right name : NVST and to set the miner's fees to 0.0008 BTC or higher.
i used this tool two times. and all that has been sweep is 0.00000009 NVST.
Send Asset Quantity
MAX transfers entire balance.
thats what i did.
EDIT:
I had to put the exact amount of coins to be able to sweep everything.