Do NOT use lacquer thinner or any other solvent. It can penetrate the Proseal around your rivets. And while it might not cause paint blisters now, in a coupled of years it probably will.
Hi,
I needed to do this for a leaky tank baffle; I haven't tried the Vans stuff but if you can obtain some 'Skyrestore' from https://www.socomore.com ? Surface preparation ? Sealant removal
This does the job, although you need several applications to remove a little at a time- it's quite time consuming.
The only chemical that will touch cured Proseal is MEK. It is horrible, nasty stuff, be very careful. Use a mask and gloves. Cut off as much as possible then use MEK on a rag to rub off the residue, use it sparingly.