Darren - The easiest way is with a premium paint stripping solution. Unfortunately though, their effectiveness varies from brand to brand and in different situations there isn’t one that’s always guaranteed to work. It’s often a case of trial and error and in 30 years I’ve yet to find one that performs as well as claimed.
The brands I would recommend are ‘Peelaway’ or ‘Rustins Strypit’ – don’t expect any miracles though. DIY store’s own brands are generally useless and a complete waste of money.
An electric powered heat gun can often be the easiest way and, when you consider the cost of multiple packs of chemical strippers, can be the most economical.