Puppy pads are good as are picnic blankets that have a waterproof underside.
Here’s a link to all the waterproof throws/blankets available on the UK store.
https://www.lovehoney.co.uk/search?q=Blanket&searchButton=suggestion&lang=en_GB
Every single time my partner makes me squirt, either with his fingers, or during sex.
It’s never happened for him before, so was fun when he found out I can.
Helps if you have long fingers, or get into a position where his 
is pointing towards your bellybutton, or use the lovehoney, which can be used for male prostate, or female squirting.
Won’t work as well first thing in the morning if your super dehydrated
So I don’t want to just delete a load of the wiki without putting it on here first, but there’s a section to it which states you need to stimulate the g-spot to squirt, but this contradicts and earlier part which correctly identifies that clitoral stimulation can help achieve squirting.
Theres a really helpful peer reviewed article here which is a review of a whole body of evidence around squirting and female ejaculation, and explores the differences between the two things.
A lot of the wiki is of course correct, but there are a lot of outdated ideas out there still about g-spot arousal, needing penetration, and what the clitoris actually is.
My partner always squirts when I insert my 2 middle fingers and claw / rub her g spot. My other hand rests on her pubic bone with my thumb rubbing her swollen clit. She always pops like a cork 