need more help to refinish exterior door

[imianga]

I just purchased RO150 and want to use it for refinishing an exterior wooden door.
It has not been maintained for several years and previous finish is in bad condition.
I planning to sand it out starting with 100 grit upto 180grit, then put some oil varnish mixture.
Should I start with 80 grit?
Also what kind of finish do you recommend for harsh weather condition?
It is very dry and hot during summer...long winter with a lot of snows in my area.
Someone recommend me to go with light finish and maintain more often rather than putting thick finish

Thanks

 

[greg mann]

I would start with 100 grit in rotex mode and about 4 on the radio dial. If that gums up with the old finish or is too slow then drop down to 80 grit. Cristal is a good place to start if you have it. My $.02