It sounds like youre doing it the way I do maps. I know 99-100 is 400ish maps so I prerolled them all in a stash tab and search for reflect. I think a lot of people make the mistake of using sextants, chisels etc too early which in the end doesnt matter unless you're pushing 100. This is what I do below and beyond ALL maps.
1-96, alch and rip (no reflect)
97 - Chisel, run 1-2 sextants dont reroll (no reflects)
98 - Chisel, 4+ sextant rerolling slipstreams or stationary dmg etc (no reflect, no -max res.)
99 - Chisel, 4+ sextant, 3 frags (no reflect, -max res, no 2 elements of dmg at once)
100 finally done, it wasnt as bad as I thought with the density in UGS. I maintained 45m xp/hr at 98-99 and maintained 36m-39m xp/hr at 99. This is by far the highest amount of XP I have ever gotten grinding and the most per hour. More than doing 100 in legacy league with broken items and 8 sextant shores.