Seen many canvas modelled using kitchen towel or similar washed in Pva.
As an alternative try drying out wet wipes. 

 These are material and tougher to rip. 

To soak them  use a mixture of a some water, paint to colour and  bath sealant.  Squeeze some Sealant into container, A small amount of water paint mix, shake it till Its bubbly.  Paint   it on,as it dries the canvas will be able to hold shapes.  Saw this on youtube in relation to Armour modelling….it works!

Gary