I've seen some bottles of solvent that had a half inch of crud in the bottom from dunked brushes or patches.
Uncapped ammonia based solvents evaporate quickly leaving only a weak carrier.
These plastic blow moulded pipets are just the ticket for dispensing fluids onto patches, or lubricating a tight spot. Keep your bottle of solvent fresh, and capped. Reduces risk of spilling while you dispense fluids from the pipet onto the patch. This controlled application of highly volatile solvents keeps the concentration of vapors down, and reduces contamination of your source bottle. The bulb prevents solvent from leaking until you apply a little pressure.