The lacquer should be allowed to fully harden which will take at least 2 weeks, before using rubbing compound on overspray or to blend into existing paintwork

We have spoken to the manufacturer at length on this product and they have informed us of the following
Its always hard to diagnose a problem from a description of it (without actually seeing it). However, in this case, it sounds like application technique. The can is obviously OK, as the customer was happy with the first coat. So, either the second coat has been applied too dry - can held too far away, or, the overcoating window has been missed. It is possible that the ""little blobs"" that can seen is the first coat starting to wrinkle.
They think the Petrol Resistant Lacquer is a great product, however it does have one big disadvantage in that it is not repairable. It does not like to be re-coated outside the strict overcoating window specified on the can. This means the whole lot will have to come off. Any residual lacquer left on the tank will show itself by wrinkling up when a replacement coat is applied. Rather than simply rub the lacquer down and re-coat, my advice is to rub the lacquer OFF, then re-coat.
Of course, if you feel you have a faulty can, you can send it back to us to have a look at.............

We have spoken to the manufacturer at length on this product and they have informed us of the following
Its always hard to diagnose a problem from a description of it (without actually seeing it). However, in this case, it sounds like application technique. The can is obviously OK, as the customer was happy with the first and second coats. It sound like the overcoating window has been missed.
They think the Petrol Resistant Lacquer is a great product, however it does have one big disadvantage in that it is not repairable.
It does not like to be re-coated outside the strict overcoating window specified on the can. This means the whole lot will have to come off. Any residual lacquer left on the tank will show itself by wrinkling up when a replacement coat is applied. Rather than simply rub the lacquer down and re-coat, my advice is to rub the lacquer OFF, then re-coat.

No Halfords Petrol Resistant Lacquer 300ml is not suitable for this type of application.

Yes the Petrol Resistant lacquer can be used over ordinary lacquer.
Just need to make sure that the ordinary lacquer has been allowed to dry thoroughly (overnight) first.

Heat will certainly speed up the curing but you also run the risk of making the lacquer wrinkle.
We always recommend curing at ambient temperature and the lacquer is petrol resistant after a few days.
If you wish to proceed with accelerated curing try a slightly lower temperature, around 50c for 24 hours. However we must stress that it could cause wrinkling and we cannot guarantee that it will be fully petrol resistant after the 24hr period. Test the process on a piece of scrap metal first.

A light sanding with 1200 grade wet & dry paper will suffice.

We have received the follwoing comment from the manufacturers of Halfords Petrol Resistant Lacquer 300ml (Cat code: 768697)
"This has been formulated for use with the Halfords range of acrylic finishes. This product has never been tested over cellulose but I would expect it to be OK. However I recommend the customer tests in a small area first to be sure."

This is based on a modified alkyd resin. It can be applied over fully cured acrylic clear coats. Follow the re-coating instructions on the can closely.