I clean my wax iron every week to keep the buildup of old burnt wax off the base of the iron. I do this by polishing the iron base plate with 220 grit sand paper. Followed up with a bit of old used up fibertex to further polish the iron base.
Once you are satisfied, to complete the job, use some old scraps of wax to rub down the iron base and wipe off with a paper towel. This last step should be done with the iron on a warm enough setting to melt the wax and repeated as needed.