Yes you can thin it with cellulose thinners.
Rate really depends on several factors; type of wood, size of piece being coated etc. basically it's a case of experimenting and developing your own preferred method of using it.
The main problem with using sealer undiluted is that on larger items you are likely to get uneven absorbtion, runs and streaking build up if you try to burnish it.
Try diluting it 20-30% for starters, sometimes I go as far as 50%.
I personally find it easier to apply more than one coat of thinned sealer (cutting back between coats) to obtain an even coat/finish than one thick coat.
I sometimes apply with cloth whilst stationary and continue to burnish finish with still wet cloth whilst rotating. (usually small items)
On larger items I use a paint brush to apply diluted (Quicker and better for the hands)
I store the brush in the bottle of diluted sealer so that it does not dry out.
A couple of links showing
diluted sealer and
Brush in use.