How do you put the bottom of the Dust Seal into the caliper when the Dust Seal is on the piston? OR, is the Dust Seal first put on the caliper and then the piston is put through the Dust Seal? That looks difficult.
Youtube is a great source of information. You have to be selective, but you can generally find someone who has tackled your job before. I have seen (and used) a technique where compressed air is used to inflate the dust cover after it is fitted, but the link below shows how to do it simply by hand.
No1. You do not want to use the piston you have pictured, it is all pitted on the side. That is a recipe for disaster and brake fluid will seep past the seal when it is adjacent to the pits.
No2. If you build the caliper like that, and it works initially, it will only be a matter of time until those pits enlarge, due to corrosion.
No3. I only use red rubber grease to lubricate the seals. Then the piston just slips into the bore with MINIMAL pressure exerted by your 2 thumbs.
Do the job correctly old son, your life and that of your passengers depend on your work.
Leslie
Expert brake builder
That was a good film on how the Dust Seal was inserted. I will get new pistons.