You can also use soapy water on your finger to tool the sealant, I prefer this over mineral spirits. You will want to have mineral spirits though, for clean up.
They do make removal tools, I've yet to find one I care for. I don't remove the old stuff unless it's peeling off, then I carefully cut around it with a utility knife and scrape it off with a plastic scraper. It doesn't need to be perfect, Proflex has some serious adhesion. Most of time you will just find little cracks or voids, those I usually just touch up. The masking tape is good advice, helps keep everything nice and neat, I use painters masking tape, as it peels off w/out leaving any sticky residue. Make sure to remove this as soon as you are done tooling the sealant.
2013 Starcraft Travel Star 229TB
2011 Jayco X17Z(traded in)
2010 Jayco Jay Series 1207(traded for the 17Z)
2011 Chevrolet Silverado 2500HD Z71 CC 6.0L/3.73
Reese "Pro Series" 800lb Trunnion WDH w/sway control