I use Multi Gyn to help prevent and treat thrush I find Canetson really burns when I use it. The HRT should actually help reduce thrush outbreaks as the oestrogen can help to maintain the acidic balance in the vagina that will reduce the chance of thrush. If you are prone to thrush then daily use of Multi Gyn helps to prevent outbreaks and it may be worth looking at your diet e.g. high sugar intake can make things worse. Eating live yogurts every day can be beneficial and the 'be kind to your bits' regime is essential - cotton knickers, nothing perfumed, wash only with special intimate washes or aqueous cream (strictly no soap), take showers not baths, no tight trousers etc.
I'd use a big dose of Multi Gyn up inside morning and night for 2-3 days to see if it helps.
DG x