Dorman and Astoria both sell their Tools to Garages so someone Business out there must be doing the Boot Replacements.
I would re-boot My Axles again if I need to. But, used one of the 2 types of Tools that were made for the Job; not a Automatic Transmission Funnel.
I had My on adventure and had more trouble with the Dorman Pneumatic Tool than the Simpler Cone Tool (was about $28) made for the Job. (Astoria Flexx Boots seem to be more popular but I used the Dorman ones.)
CV Boot Installation Problems with Dorman Pneumatic and Cone type Boot Installation
http://www.peachparts.com/shopforum/diesel-discussion/317950-cv-boot-installation-problems-dorman-pneumatic-cone-type-boot-installation.html
See Pic. If your Axle near the Differential has Bolts going through it you have an Annular Axle and do not need to Stretch Boots over the Axle. The end with the Bolts comes apart and there is a Snap Ring inside you remove and the Axle comes out of it and you can easily remove and slide new Boots on.