Yeah, aluminium wire seems to be quite touchy. You can get a few different grade wire spools though, which vary in how soft they are. The hard wire seems to go ok in a machine which isnt setup so well. But for the softer wire youd want either a proper push-pull gun or a nice short lead with a good condition plastic liner.

Getting hot tacks on aluminium, I find, is similar learning to TIG weld aluminium. You need to get the right balance between being hot enough, but quick enough to not burn through it. While still trying to not get burn backs and clogging the tip (which will probably happen 50% of the time on an average machine)