Adiseal can be cold applied.
How to seal felt roof.
Apply some bitumen adhesive over the repair and beyond to suit the patch and apply it.
Press down the top layer into the adhesive.
Cut a piece of new felt to use as a patch big enough to give above a 50mm 2 inch overlap beyond the repaired blister.
Here is a video on how to seal a flat roof permanent it does not required a lot of skills just time to let it dry completely hope it beco.
Adisolve solvent cleaner is the ideal product to clean remove oil grease tar bitumen many other stubborn deposits.
To stick roof felt shingles make sure the surface where the adhesive will be applied is thoroughly cleaned.
Use a brush to remove any loose debris.