It takes 3X AAA batteries , please unscrew the bottom and there is battery holder placed inside the torch , for better result please use a alkaline batteries
please to take a tiny bit of sample of the glue and test the glue , after curing it should go like soft gel , torch would cure the glue but for full cure,leave it under direct sunlight for 12 hours , even on a cloudy day it still cures .
and also thinner the layer better the result
For cleaning the glue residue, you can use following solutions
1) coleman fuel ( it is a black plastic bottle with red and white label any garden centres in uk sell them )
2) ronsonol lighter fluid yellow tin (not zippo)
( those two items listed above contains high percentage of PETROLEUM ETHER for samsung and iphone models it cleans without any problem
but some models of google nexus and they use different types of adhesive it won't clean )
If you can't get hold of those two listed above
3) isoproply alcohol (rubbing alcohol ) bit hard for iphones but better for samsungs
4) diluted acetone
And also thinner the layer better the result