though I'm less impressed than I wanted to be with the bootlace crimps I bought for it,
The best crimping tool I have found is this style.

https://www.ebay.co.uk/itm/353421516...Cclp%3A2334524

On the very small size i usually crimp it then rotate it a few degrees then crimp it again.

Also then is an adjustment on the tool to make a tighter crimp