Hi, well I am very surprised Thor tech support suggested using Silicone caulk on your exterior window trims. Most RV folks recommend not using any silicone sealants at all.....but each to his own.
I have used Geocel Proflex RV caulking and it is sticky and "unforgiving" stuff to apply if you are not careful or experienced using it. If you try it practice on something else first before your coach. I found taping off the line area on both sides where you did not want sealant and using neoprene/rubber gloves a must with this stuff. Also a little soapy water in a small container at the ready to smooth the caulking run with a wet finger tip; and only do a couple feet at a time or by the time you come back to smooth it out it is already starting to skin over. I know folks on this forum that also use this caulk and swear by it......but I hate applying it.....just seems like the right stuff for RV's though. I am sure others will make recommendations.....there are those that apply easy but do they last in blazing sun and freezing temps? When you have water coming in something on hand to stop it now is better than doing nothing IMO (famous last words).